[TASK] Clean up various code pieces

* TSFE->contentStrReplace only calls a hook, which is now moved to the
callers code (which only contains another hook as well)
* TSFE->clearPageCacheContent_pidList() is not used anymore (protected)
* cObj->decryptEmail() is not used anymore (protected).
* BE_USER->getRealUserId() is not used anymore (protected)
* DataHandler->recUpdateAccessCache is not used anymore (protected)
* LiveSearch (internal) -> getRecordTitlePrep() is not used anymore

Resolves: #90785
Releases: master
Change-Id: Idf14c9185a9356091ec0400faecfc8bbe5861c3b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63795


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Susanne Moog <look@susi.dev>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Susanne Moog <look@susi.dev>