[TASK] Streamline SetupModuleController

The patch gives SetupModuleController some love by
adding a first template for the outer module HTML,
cleanup up various internals along the way, and
switching to new backend templating strategy.

Resolves: #96776
Related: #96730
Releases: main
Change-Id: Ia97808ed040e65cd1311b7dfd0c1c71d6e3aebed
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73340


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>