[BUGFIX] Enable ContextMenu for file mounts and file storages again

The custom ContextMenu ItemProviders for sys_filemounts
and sys_file_storage are removed as they never worked,
because they extended the FileProvider, which uses
the combined identifier as record identifier instead of
the records uid. Also their $itemsConfiguration does not
make any sense. In the end, there is no reason to treat
those record types differently than the rest.

Resolves: #90921
Releases: master, 10.4
Change-Id: Ifd24755455d75d781a7caefa808a8b87318ca487
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69800


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>