[random test failure] CommentPreviewTest::testCommentPreview

Whilst we're only trying to fix CommentPreviewTest::testCommentPreview here, this means making changes in \Drupal\user_hooks_test\Hook\UserHooksTest.
In turn, those changes affect the following tests:

\Drupal\Tests\comment\Functional\CommentPreviewTest::testCommentPreview
\Drupal\Tests\user\Kernel\UserEntityLabelTest::testLabelCallback
\Drupal\Tests\user\Functional\UserEditTest::testUserEdit
\Drupal\Tests\user\Functional\UserTokenReplaceTest::testUserTokenReplacement

So I think we have to run our multiple-run tests on all of them before and after the chage.

MR !10711 Has some pipeline changes to make those tests, and only those tests, run 2500 times and gives us 28 fails out of the 2500 runs. Those fails are all in \Drupal\Tests\comment\Functional\CommentPreviewTest::testCommentPreview

MR !10712 shows that changing \Drupal::state()->set()/get() to Drupal::keyValue()->set()/get(); passes a 2500 times run on all four mentioned tests without errors.

The changes we want committed after review are in MR!10713

Based on the other one reviewed and merged this seems like a good refactor.

One question on the MR.

Tried to answer in thread

For 1 open thread

If you are another contributor eager to jump in, please allow the original poster @spokje at least 48 hours to respond to feedback first, so they have the opportunity to finish what they started!

I'm not getting anywhere with the remark in the MR, so throwing it out in the open for other, bigger brains.

spokje → changed the visibility of the branch 11.x to hidden.

Believe all feedback has been addressed on this one.

catch → closed merge request !10713

Committed/pushed to 11.x and cherry-picked back to 11.1.x.

This doesn't apply to 11.0/10.5/10.4 due to OOP hooks, moving to 'to be ported'.