Move system/base component CSS to respective libraries where they exist

The MR will fail because library-overrides and possibly test coverage will need updating, but did a before/after with devtools moving just progress.module.css for now.

Before: 2.9kb transferred over network, resource size 9.3kb
After: 2.7kb transferred over network, resource size 8.7kb

Pushed a commit that should make tests pass. Moving to needs review - we may or may not decide to do the other two (or more) CSS files in this issue, but views on the general approach would be great.

With tabledrag and autocomplete done too:

1.8kb transferred over network, resource size 5.5kb

This is nearly half the filesize for the first CSS aggregate (standard profile anon front page) already.

Pretty sure we can also do:

AJAX progress - can be moved to drupal.ajax - this could probably be done in this issue.

      css/components/system-status-counter.css: { weight: -10 }
      css/components/system-status-report-counters.css: { weight: -10 }
      css/components/system-status-report-general-info.css: { weight: -10 }

- can make a new library for the status report and then attach from there, but no existing library - needs its own issue probably.

tablesort - we could make a new library for tablesort and move the CSS there, not sure exactly where's best to attach it from yet (TableSort.php somewhere?), so could also use its own issue.

Opened #3432245: Split system status report CSS out to its own library and #3432244: Split tablesort.module.css out to its own library and attach it via tablesort

Fixed that last Claro issue and added a change record: https://www.drupal.org/node/3432346

Tagging with sustainability because although it's a tiny change, it's likely to reduce bandwidth requirements on 99.9% of Drupal sites including for anonymous users - the only sites not affected would be those actively removing these files from the library definitions.

Now the first CSS aggregate in the standard profile/olivero for anonymous users on the front page is less than half the size both compressed and uncompressed:

Before:
Before: 2.9kb transferred over network, resource size 9.3kb

After:
1.3kb transferred over network, resource size 3.5kb

I think we should update https://www.drupal.org/about/core/policies/core-change-policies/frontend... to explicitly say that the location of JavaScript and CSS files is @internal and that libraries-override implementations may need to be updated in minor releases. I realise this is the opposite of what I said about bc circa 8.6 in #2484623: Move all JS in modules to a js/ folder but we've done a lot more minor releases since then. It might be worth grepping contrib and pro-actively opening issues for any themes affected though. Supporting two minor branches should be OK too, because libraries-override will silently ignore an override of a file that doesn't actually exist.

If we did want to implement bc for all of these, we could probably add it to LibraryDiscoveryParser directly, we'd need a mapping with something like:

$mapping = [
  'new_library' => [
     'old_library' => [
         'new_filename' => 'old_filename',
     ],
   ],
];     

Then in ::setOverrideValue() when we're applying overrides to the library, we'd look up whether there are any entries for that library, then look for any overrides of the old library, then whether any of the files match, then add those to the replacements and trigger a deprecation error. If we want to do that, should be its own issue and postpone this and similar issues on it.

I hadn't seen #2880237: [meta] Refactor system/base library, it's taking a completely different approach, which I'm not sure if it's better or worse yet - creates new libraries for each file, and adds them in the templates with the markup they correspond to. The problem here would be if a theme overrides those templates and doesn't update, then the libraries won't be loaded any more. But also if code is using those templates generically without the libraries that we're moving files to here, then it would work better. Would be good to get an opinion from someone who actually does theme things about that.

While that issue doesn't move the files, it does change the library definitions which will also break library-overrides, so I've gone ahead and opened #3432601: Add deprecation/bc support for library-overrides when files are moved to add deprecation support - if we've got that, then we don't need to discuss whether to add it or not :)

Opened a meta at #3432603: Audit the system/base libraries too, although I think we can go ahead with these couple of issues parallel to that, then audit whatever's left.

@mgifford see #13, it's already saving 1.6kb compressed, 6kb uncompressed and there are at least four more files we can stop loading on every request in follow-up issues.

I've got working deprecation support up at #3432601: Add deprecation/bc support for library-overrides when files are moved now.

Went ahead and added the moved_files entities here now that #3432601: Add deprecation/bc support for library-overrides when files are moved is RTBC.

Discussed this with @nod_ in slack and he preferred merging the files into the existing libraries rather than creating new ones, so keeping going with the approach here. We can repurpose #2880237: [meta] Refactor system/base library once this lands for what's left.

I've added asset file size support to performance tests over in #3436527: Record total css and js file size in performance tests.

I also added a draft MR on that issue, combining the test coverage with the changes here, so we can see the difference in the test coverage, the test changes as a result of that are here:
https://git.drupalcode.org/project/drupal/-/merge_requests/7231/diffs?co...

diff --git a/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryAuthenticatedPerformanceTest.php b/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryAuthenticatedPerformanceTest.php
index d623c59a90..af01bf3fe0 100644
--- a/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryAuthenticatedPerformanceTest.php
+++ b/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryAuthenticatedPerformanceTest.php
@@ -36,7 +36,7 @@ public function testFrontPageAuthenticatedWarmCache(): void {
       $this->drupalGet('<front>');
     }, 'authenticatedFrontPage');
     $this->assertSame(2, $performance_data->getStylesheetCount());
-    $this->assertSame(47552, $performance_data->getStylesheetBytes());
+    $this->assertSame(44966, $performance_data->getStylesheetBytes());
     $this->assertSame(1, $performance_data->getScriptCount());
     $this->assertSame(132038, $performance_data->getScriptBytes());
 
diff --git a/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryFrontPagePerformanceTest.php b/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryFrontPagePerformanceTest.php
index 36590df28c..5f3fbff2c4 100644
--- a/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryFrontPagePerformanceTest.php
+++ b/core/profiles/demo_umami/tests/src/FunctionalJavascript/OpenTelemetryFrontPagePerformanceTest.php
@@ -66,7 +66,7 @@ public function testFrontPageHotCache() {
     $this->assertSame(1, $performance_data->getScriptCount());
     $this->assertSame(7075, $performance_data->getScriptBytes());
     $this->assertSame(2, $performance_data->getStylesheetCount());
-    $this->assertSame(45495, $performance_data->getStylesheetBytes());
+    $this->assertSame(41556, $performance_data->getStylesheetBytes());
   }
 
   /**
diff --git a/core/profiles/standard/tests/src/FunctionalJavascript/StandardPerformanceTest.php b/core/profiles/standard/tests/src/FunctionalJavascript/StandardPerformanceTest.php
index bdfe1ff949..4c1964afca 100644
--- a/core/profiles/standard/tests/src/FunctionalJavascript/StandardPerformanceTest.php
+++ b/core/profiles/standard/tests/src/FunctionalJavascript/StandardPerformanceTest.php
@@ -55,7 +55,7 @@ public function testAnonymous() {
     }, 'standardFrontPage');
     $this->assertNoJavaScript($performance_data);
     $this->assertSame(1, $performance_data->getStylesheetCount());
-    $this->assertSame(7434, $performance_data->getStylesheetBytes());
+    $this->assertSame(3495, $performance_data->getStylesheetBytes());
 
     $expected_queries = [
       'SELECT "base_table"."id" AS "id", "base_table"."path" AS "path", "base_table"."alias" AS "alias", "base_table"."langcode" AS "langcode" FROM "path_alias" "base_table" WHERE ("base_table"."status" = 1) AND ("base_table"."alias" LIKE "/node" ESCAPE ' . "'\\\\'" . ') AND ("base_table"."langcode" IN ("en", "und")) ORDER BY "base_table"."langcode" ASC, "base_table"."id" DESC',
@@ -111,7 +111,7 @@ public function testAnonymous() {
     }, 'standardNodePage');
     $this->assertNoJavaScript($performance_data);
     $this->assertSame(1, $performance_data->getStylesheetCount());
-    $this->assertSame(7159, $performance_data->getStylesheetBytes());
+    $this->assertSame(3220, $performance_data->getStylesheetBytes());
 
     $expected_queries = [
       'SELECT "base_table"."id" AS "id", "base_table"."path" AS "path", "base_table"."alias" AS "alias", "base_table"."langcode" AS "langcode" FROM "path_alias" "base_table" WHERE ("base_table"."status" = 1) AND ("base_table"."alias" LIKE "/node/1" ESCAPE ' . "'\\\\'" . ') AND ("base_table"."langcode" IN ("en", "und")) ORDER BY "base_table"."langcode" ASC, "base_table"."id" DESC',
@@ -146,7 +146,7 @@ public function testAnonymous() {
     }, 'standardUserPage');
     $this->assertNoJavaScript($performance_data);
     $this->assertSame(1, $performance_data->getStylesheetCount());
-    $this->assertSame(7159, $performance_data->getStylesheetBytes());
+    $this->assertSame(3220, $performance_data->getStylesheetBytes());
 
     $expected_queries = [
       'SELECT "base_table"."id" AS "id", "base_table"."path" AS "path", "base_table"."alias" AS "alias", "base_table"."langcode" AS "langcode" FROM "path_alias" "base_table" WHERE ("base_table"."status" = 1) AND ("base_table"."alias" LIKE "/user/2" ESCAPE ' . "'\\\\'" . ') AND ("base_table"."langcode" IN ("en", "und")) ORDER BY "base_table"."langcode" ASC, "base_table"."id" DESC',

As you can see with the standard profile it's a reduction of about 50% the filesize for the CSS aggregates, with Umami it's a reduction of more like 10%.

However this is issue is only the very easiest changes, if we finish #2880237: [meta] Refactor system/base library I think we could be looking at more like a 20% reduction in CSS payload on Umami, which should be comparable with at least some real themes and sites.

Bumping this to major given the numbers.

Poking around in here I also found/opened #3436855: Remove the views-align-* CSS classes.

Being optimistic and tagging this for release highlights, with some other issues we've got enough for a short performance improvements section.

Tried a lighthouse report on olivero to see how we score for unused CSS and how much this issue improves it. It's not much unfortunately, but then discovered that Olivero's own global styling library includes tabledrag.css rather than using libraries-extend. I've added a commit to change that too.

Is Rector capable of working with theme info files to update the paths automatically for upgrading users?

That's a good question and the answer is no because moved_files only exists since last week, but I opened a feature request against rector #3438038: Support the new 'moved_files' key for updating libraries_overrides.

Test coverage in #3436527: Record total css and js file size in performance tests landed so we can now update that test coverage to show the improvement here.

@nod_ agreed with should move more things out, but #2880237: [meta] Refactor system/base library, #3432603: Audit the system/base libraries and #3432244: Split tablesort.module.css out to its own library and attach it via tablesort are already open. I already worked on #3436527: Record total css and js file size in performance tests and #3432601: Add deprecation/bc support for library-overrides when files are moved since this was last RTBC, and would prefer not to increase the scope here any more. Definitely planning to continue once this lands though.

Added a note on #2880237: [meta] Refactor system/base library to make sure those two get included.