[TASK] Synchronize RST files

* Various .rst file index fixes, NotScanned usually does not make
  sense on Important- and Feature- files.
* Add a missing extension scanner config
* Sync 7* and 8* folders to other core branches

Resolves: #84141
Releases: master, 8.7, 7.6
Change-Id: Ifc19d774d45395cb30bd51f50d9121af409f48bb
Reviewed-on: https://review.typo3.org/56012


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>