[BUGFIX] Add required column "extension" in TCA of sys_file

This is required in order the Vidi search to work.
Vidi has to known the type of the field, "input" in this case.

Change-Id: I665e939ea92693ece4d3f32cb1410d8653b4ee16
Releases: 3.0.0
Resolves: #59082
Reviewed-on: https://review.typo3.org/30373
Reviewed-by: Fabien Udriot
Tested-by: Fabien Udriot