[TASK] Move FrontendBackendUserAuthentication into EXT:frontend

Since FrontendBackendUserAuthentication, required for executing
the Frontend request process, has only dependencies to EXT:frontend
and EXT:core it is now moved to EXT:frontend.

Resolves: #105175
Releases: main
Change-Id: Ib04e7d1e7a47b00b32d9c477cb7cdb47238b158e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85901


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>