[TASK] Streamline PageRenderer class

Some methods are not in use anymore, and also
some FQCN can be shortened in order to
clean up this class for further refactorings.

Resolves: #88673
Releases: master
Change-Id: I642caec9386945d0217984b76f586a9a24e13d14
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61214


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Alexander Schnitzler <review.typo3.org@alexanderschnitzler.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Sven Juergens <typo3@blue-side.de>
Reviewed-by: Alexander Schnitzler <review.typo3.org@alexanderschnitzler.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>