[TASK] Declare all test classes final

Test classes should never extend each other.
phpunit 10 is also a bit more picky about naming
of abstract test cases.

The patch adds a script to verify all test case
files are declared final, adds it to CI, and
adapts existing tests accordingly.

> Build/Scripts/runTests.sh -s checkTestClassFinal

Change-Id: I07581bffebe42a82fafc56a9bc6cae7c46508b1a
Resolves: #100544
Releases: main
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78460


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>