[!!!][TASK] Remove deprecated TSFE hooks and output functionality

This change removes deprecated hooks and methods from TSFE
related to output:

* TSFE->isOutputting()
* TSFE->processContentForOutput()
* TSFE->settingLocale()
* $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/class.tslib_fe.php']['hook_eofe']
* $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/class.tslib_fe.php']['pageIndexing']
* $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/class.tslib_fe.php']['isOutputting']
* $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/class.tslib_fe.php']['tslib_fe-contentStrReplace']
* $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/class.tslib_fe.php']['contentPostProc-output']

Resolves: #91476
Releases: master
Change-Id: I2711924dce00ad2cd1ec9a236d8fde9da0105a65
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64583


Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>