[TASK] Set locale for requests earlier in Frontend process

Due to non-site handling, setting the locale was built on top of
TypoScript settings. This was the reason, this was encapsulated
within "$TSFE->settingLocale()".

However, as the locale is now always available once SiteLanguage
has been resolved, this can be handled very early.

On top, the functionaltiy can be extracted from TSFE completely,
and be universally used within "Locales".

The method $TSFE->settingLocale() is now deprecated.

Resolves: #88473
Releases: master
Change-Id: I28c057ecc6d6ba37153a09812a61e5827cdb7bc5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60863


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>