[TASK] Streamline TSFE/RequestHandler for "Page Generation"

Various documentation in TSFE is updated,
in addition to having $TSFE->setAbsRefPrefix()
to be set within the postProcessing to overcome
issues when the call is forgotten in custom
TSFE instances.

Resolves: #88555
Releases: master
Change-Id: Ib3ce22db1e6ce7b0985d486d584c26f25755efa4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60998


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>