[TASK] Deprecate inline localizationMode

TCA type's inline localizationMode can either be "keep" or "select".
At least "keep" is counter-productive if allowLanguageSynchronization
is enabled. That's why the whole localizationMode behaviour setting
shall be deprecated and ignored in case allowLanguageSynchronization
is enabled for the very same TCA field.

This change does not migrate non-conflicting localizationMode settings
automatically, since this potentially might be breaking and cannot be
done without side-effects. Besides that calls to the static function
BackendUtility::getInlineLocalizationMode() do not trigger a new entry
in the deprectation log since the usage of localizationMode in TCA is
logged already.

Resolves: #79770
Releases: master
Change-Id: Ic2072877d08bb880e9e957d6d31f0527333c2cc5
Reviewed-on: https://review.typo3.org/51650


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Sommer <markussom@posteo.de>
Tested-by: Markus Sommer <markussom@posteo.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>