[BUGFIX] Add UID of metadata to mergedProperties

As UID of sys_file and sys_file_metadata are ambiguous
the UID of meta data is accessible with key
metadata_uid now. That way UID of sys_file_metadata
is accessible in mergedProperties, too.

Resolves: #92010
Releases: master, 10.4
Change-Id: I6fa7dedb793fb0f0e0027be60fe8e16fe93b9862
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65332


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Jörg Bösche <typo3@joergboesche.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Benni Mack <benni@typo3.org>