[TASK] Move documentation files into 9.4 folder - part 3

The change also contains some documentation related improvements
in some code files, where the need occured.

Change-Id: I346fd70e20bd0765ac4cc663dc7e3fd73d02651b
Resolves: #86075
Releases: master
Reviewed-on: https://review.typo3.org/58166


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>