[!!!][TASK] Migrate file edit form to FormEngine

To simplify the overhaul of EXT:t3editor, the form to change a file's
content is based on FormEngine now.

Additionally, the file rename form has been streamlined to the overall
backend visual appearance.

Resolves: #81763
Releases: master
Change-Id: Ifb9bc5513bff923a6d4cdbcb6046e87f4dcf3626
Reviewed-on: https://review.typo3.org/53129


Tested-by: TYPO3com <no-reply@typo3.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>