Consolidate ckeditor5's FunctionalJavascript tests

This moves around half the methods in the test to protected methods - mostly the ones that don't change any configuration. On my local ddev it reduces runtime from just under 3 minutes to around 2m 30s, but it's very different on gitlab with concurrency - hopefully can get an idea from the test run.

Doesn't reduce the overall job time yet, but finished seventh from last on https://git.drupalcode.org/project/drupal/-/jobs/2210968

SourceEditingTest completing in about 1/6 the time with a foreach loop instead of a data provider.

Before:

../vendor/bin/phpunit modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php 
PHPUnit 10.5.26 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.8
Configuration: /var/www/html/core/phpunit.xml

......................                                            22 / 22 (100%)

Time: 02:24.161, Memory: 6.00 MB

After:

../vendor/bin/phpunit modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php 
PHPUnit 10.5.26 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.8
Configuration: /var/www/html/core/phpunit.xml

..                                                                  2 / 2 (100%)

Time: 00:23.510, Memory: 6.00 MB

https://git.drupalcode.org/project/drupal/-/jobs/2211630 down to 3m26 seconds from around 4m10s now.

This one took a little longer to review but don't believe any coverage has been lost.

nod_ → closed merge request !8899

Committed and pushed 2d94b30e56 to 11.x and a43be0945b to 11.0.x and a8ea546de2 to 10.4.x and c598215b8c to 10.3.x. Thanks!

Automatically closed - issue fixed for 2 weeks with no activity.