[TASK] Use PSR-7 Request in BackendController

Various GeneralUtility::_GET() calls are now replaced by
using the PSR-7 Request object, reducing the need for accessing
global scope variables $_GET and $_POST.

Resolves: #90655
Releases: master
Change-Id: Ia636df18396f27db5edab3533371d25d98324831
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63559


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>