The functionality to handle TypoScript
overrides for Labels is now moved
from Extbase LocalizationUtility
to LanguageService.

All tests now use proper XLF files
and also real TypoScript values,
in order to make the tests easier to
understand.

Instead of magic $LOCALLANG and $LOCALLANG_UNSET
properties, LocalizationUtility now keeps
the actual LanguageService objects in its storage.

The LanguageService->overrideLabels() method should be
used with care, as other instances of the object might
not have the overrides stored.

Resolves: #99559
Releases: main
Change-Id: I3e83695baebec545b5e6c5d8504df95950a543cc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77399


Tested-by: core-ci <typo3@b13.com>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>