[!!!][TASK] Remove support for FE_SESSION_KEY session transfer

A seldom used (and undocumented) feature to transfer a session
via the GET parameter FE_SESSION_KEY is removed in favor
of custom authentication services when integrating third-party
Single-Sign-On processes.

Resolves: #93002
Releases: master
Change-Id: I8418bdf36ce3dd2ab63edb9a77f2db59beeaac43
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67035


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>