[TASK] Cleanup CLI commands in EXT:backend

* Make backend:unlock and backend:lock a separate class.
* Manually require the CLI user for ReferenceIndexUpdateCommand
* Cleanup the commands.php (as the "user" property is not evaluated anymore)

Resolves: #79261
Releases: master
Change-Id: Id3c90780de0dc299c07c5bca14dd4247b634d53c
Reviewed-on: https://review.typo3.org/51247


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>