[FEATURE] Improve Usage and Variant Grid Render

Column Usage in the Grid displays also information
of a File related to the RTE.

Change-Id: I1fa831501962b154399cbdf4184cadaa70864c01
Releases: 2.0.0
Resolves: #48869
Reviewed-on: https://review.typo3.org/26338
Reviewed-by: Fabien Udriot
Tested-by: Fabien Udriot