[BUGFIX] Fix typing issues in various backend controllers

This change aims to reduce all left-over strict type changes,
and backwards-incompatible changes in our own code base
making sure that TYPO3 can run smoothly with PHP 8.

Resolves: #94335
Releases: master
Change-Id: I9d1c8966a56a80bb68216ae535547e0bf55e50c9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67243


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>