[TASK] Remove extbase Request isCached() and setIsCached()

To further prepare towards a PSR-7 Request in extbase
we have to get rid of as many setters as we possibly can.

Both methods isCached() and setIsCached() were marked
@internal in v10 and related to extbase internal handling.

Internal usages have been dropped when extbase introduced
PSR-7 Responses with #92502, the methods can be dropped now.

Change-Id: I1b72cef669e4bc6bd75cac855bfb18fa47663b63
Resolves: #94319
Related: #94228
Related: #94231
Related: #94223
Related: #92502
Releases: master
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69466


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>