[FEATURE] Add feature toggle interface to Settings

Admin tools -> Settings is extended by a GUI to manipulate
feature toggles. Note this interface lists only core features
at the moment since extensions currently have no way to
extend DefaultConfigurationDescrition.yml with additional
information.

Resolves: #85894
Related: #83429
Releases: master
Change-Id: I7ae03c87f2bf94281d4d63d2ff80c6f0460807cb
Reviewed-on: https://review.typo3.org/57952


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>