[TASK] Deprecate flushByTag hook

The hook
$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/cache/frontend/class.t3lib_cache_frontend_abstractfrontend.php']['flushByTag']
is deprecated, since it contradicts the recommended
way for custom cache functionality, which is
to implement a custom cache frontend using
the corresponding Frontend API.

Resolves: #99592
Releases: main
Change-Id: Idb158c29408d5335774986adfb351e231f855a9d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77464


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>