[TASK] Calculated hash of File object is never used

The indexing pre-calculates the file hash and stores it in
the sys_file table. Sadly the getter of file objects never looks
at this again and always recalculates the hash via the driver,
which is very slow.

Resolves: #54235
Releases: 6.2, 6.1, 6.0
Change-Id: I16bfa2126031f26b8e31da8d8c0b3fc07d0217dc
Reviewed-on: https://review.typo3.org/26689
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader
Reviewed-by: Oliver Klee
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack