[TASK] Mark various internal TSFE methods as protected

Various methods within TypoScripFrontendController
are now "protected" as they are marked as internal.

Resolves: #95315
Releases: master
Change-Id: Iae9691457b250305c617b11fa5f558ac4e55c2b8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71179


Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>