[TASK] Make GeneralUtilityTest phpunit 10 compatible

Using the test class as fixture is problematic
since the constructor changes in phpunit 10.
Refactor this and clean up a bit.

Resolves: #100401
Related: #100249
Releases: main
Change-Id: Id15be97acb967e1badd17163389583c56859b0bf
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78374


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