[TASK] Prepare cache timeout more efficiently in Frontend

Cache Timeout, configured via config.cache_period can be configured
when TypoScript is available.

The functionality $TSFE->generatePage_preProcessing() has been
thinned out further, as custom PHP Scripts are now handled via custom
RequestHandlers anyway, which now rely on this information
being set earlier (and also when a page should not be generated).

Resolves: #88475
Releases: master
Change-Id: Id9b6b0921c797e2b9de8d7b4302c515e59b0217e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60864


Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>