[FEATURE] Integrate File Abstraction Layer Indexer Task

Integrate a scheduler task that takes care of indexing files.

Change-Id: Id967456dbefadc33d1a23e8756e2cfef30f7139a
Resolves: #34284
Releases: 6.0
Reviewed-on: http://review.typo3.org/10657
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog
Reviewed-by: Tolleiv Nietsch
Tested-by: Tolleiv Nietsch
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader