[TASK] Add PSR-4 namespace integrity check for code files

This patch adds a script to scan and verify namespace of
core class and test files to be PSR-4 compliant. It uses
provided namespace registration in core system extensions
and root composer file for test namespace registrations.

Test fixture test extensions are ignored for now. Check
for these will be enabled in a dedicated patch, after
streamling of fixture test extensions has been done.

Resolves: #97790
Releases: main, 11.5
Change-Id: I36d2946891f2e12dd140b98075a13a65f0b70bb4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74957


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>