[TASK] Include test extensions into namespace integrity check

After providing full PSR-4 compliance for all test extensions,
no exception is needed anymore for the to run the integrity check.

Resolves: #100835
Releases: main, 12.4

Change-Id: Id00349f4c5baf1e4361130faa4e6a4ac45a641ea
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78963


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>