Remove Utility component BC layers

@el7cosmos thanks for talking the time to sort all this out...

1) I have visually scanned this patch and all the changes make sense to me.

2) When I search for @trigger or @deprecated in the Utilities directory

All looks clear, the hits in DeprecatedArray should remain.

3) The patch applies

4) The are no additional coding standard errors.

Patch in #5 needs a reroll.

I have re-rolled.

#9 only covered the Unicode class, this adds Crypt and SafeMarkup.

Needs a reroll, the includes removal removed one method as well I think.

Re-rolled. #3062757: Remove deprecated legacy include files from Drupal 9 was commited.

Unused class TextWrapper after we delete SafeMarkupTest. However not marked as deprecated. Can we also remove it?

core/tests/Drupal/Tests/Component/Utility/TextWrapper.php

namespace Drupal\Tests\Component\Utility;

/**
 * Used by SafeMarkupTest to test that a class with a __toString() method works.
 */
class TextWrapper {

Re #15 I think that is fine to delete, it was only ever intended for use with the companion class.,

Per a Slack discussion with Gábor Hojtsy regarding usage of D9 tags (Drupal 9, Drupal 9 compatibility, Drupal 9 readiness, etc.), "Drupal 9 compatibility" should be used for contributed projects that need updating and "Drupal 9" was the old tag for D8 issues before the D9 branch was ready. Doing tag cleanup here based on that discussion.

Addressed #17.

+++ /dev/null
@@ -1,74 +0,0 @@
- *   so that the output can can be themed, escaped, and altered properly.
- *
- * @see https://www.drupal.org/node/2549395
- *
- * @see TwigExtension::escapeFilter()
- * @see twig_render_template()
- * @see sanitization
- * @see theme_render
- */
-class SafeMarkup {

Looking at existing "SafeMarkup" references in core..

We have \Drupal\KernelTests\Component\Utility\SafeMarkupKernelTest for example. We could say that's in for the word "safe markup", but at least the class docblock has an explicit "SafeMarkup" reference. And the only thing it really seems to test is :url-style placeholders. Not sure if renaming a test and test methods is something we want to do, so maybe just the docblock?

Then we have SafeMarkupTestMarkup, a test clas in TwigMarkupInterfaceTest, but there's not really a reference to SafeMarkup, so OK?

Raised #3098244: Rename SafeMarkupKernelTest to FormattableMarkupKernelTest to handle the first part. I think that the SafeMarkupTestMarkup test class is OK, it is nothing to do with the SafeMarkup concept.

Looks good to me, we have a separate issue for that one badly named test class.

Committed 3447368 and pushed to 9.0.x. Thanks!