[TASK] Use consistent checks for USER_INT logic

A few places in TYPO3 Core do manual checks if there
are non-cacheables on a page, which could be simplified
by just using the $TSFE->isINTincScript() method.

In addition, a safer check for a NON-empty INTincScript
value is used, instead of just a typecheck of array.

Resolves: #89652
Releases: master
Change-Id: I24b2b55b3705927720e36181926cf6e752bf0f66
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62303


Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>