Provide correct display name and title for comment admin view displays

I think we should first change the comment display names since that view was just added in this release and it has two page displays that are semantically different. It's less of an issue for admin/content and admin/people since they have a single page display.

A novice contributor could probably create this patch also!

Okay view display machine names are a pet peeve of mine and it seems especially silly to ship with mystery IDs for a view we just added only to change it later (and not be able to have 8.5.x or whatever match the view on 8.4.x sites), so I rolled the patch myself.

Noticed a related bug while I was in there (the display titles do not match the case of the tabs, which we fixed already in the original patch) and then made the display machine name correlate directly with the user-facing labels.

With a screenshot to show what it's fixing in the Views UI.

The files admin view has a similar issue with the machine name, but that's less compelling to fix for 8.4.0 by tomorrow since it's been in core since 8.0.0. We wouldn't provide an upgrade path for the file admin view since it could seriously screw with people's custom code, plus we shouldn't be modifying sites' config anyway for such changes (sites own their config, not modules).

Edit: Fixed a fantastically run-on sentence.

It just needs display name updates in \Drupal\Tests\comment\Kernel\Views\CommentAdminViewTest::testFilters()

+++ b/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
@@ -0,0 +1,267 @@
+    $this->doTestFilters('page_1');
...
+    $this->doTestFilters('page_2');

I meant these.

Thanks @jibran.

Perfect!

Committed/pushed to 8.5.x and cherry-picked to 8.4.x. Thanks!