[FEATURE] FAL missing files report

Adds a report about files flagged as missing.

Resolves: #51097
Releases: 6.2
Change-Id: I95f55fe9f0da9247e6960663dd315e82e18cc2b6
Reviewed-on: https://review.typo3.org/23143
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters