[TASK] Use ServerRequestInterface in SchedulerModuleController

* replace usages of _GP, getIndpEnv
* add return hints

Resolves: #84387
Releases: master
Change-Id: I156f9005c132ab91abfbd72b97084ede6708d0dc
Reviewed-on: https://review.typo3.org/56264


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Robert van Kammen <rvkammen@hotmail.com>
Tested-by: Robert van Kammen <rvkammen@hotmail.com>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>