[BUGFIX] Do not depend on a database connection in CLI authentication

Neither the backend user authentication should try to perform
database queries, nor the extbase services.

As a side effect this allows to run the cli tool when
LocalConfiguration.php or PackageStates.php are missing,
which allows to run commands like `dumpautoload` in that case.
Note: *Only* in that case, not if a database connection
is configured, but not available – for that usecase failsafe
booting will be needed, as proposed in https://review.typo3.org/c/58298/
and/or https://review.typo3.org/c/58300/

As a drive-by we also add a null coalescing operator to
IconRegistry::registerModuleIcons() which is currently
required because ext_tables.php files are loaded in
incorrect order if PackageStates.php is missing (reported
in another bug: #86408). Although this workaround will
not be strictly required when that bug is fixed, that functions
should still properly handle that case.

Change-Id: I7d339e21160d25b5aee5dd0e2f25491a22ec83e9
Releases: master
Resolves: #86416
Related: #86408
Reviewed-on: https://review.typo3.org/58427


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>