[FEATURE] Add submodule for filemounts

Adds a submodule to the beuser module, which provides an
overview over all filemounts and allows them to modify,
hide, delete and add those.

Resolves: #99038
Releases: main
Change-Id: I2769ad34562c0428226da4abe1ab79077fc52475
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76547


Tested-by: core-ci <typo3@b13.com>
Tested-by: Susanne Moog <look@susi.dev>
Reviewed-by: Susanne Moog <look@susi.dev>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>