[TASK] Cleanup code imports for all workspaces classes

The system extension workspaces was never touched in terms of
checking if actually methods are needed, and a lot of code still uses
FQDN instead of the "use" keyword for a PHP class.

Some unused dependencies (e.g. to Extbase's objectmanager) are
removed as well.

Resolves: #84136
Releases: master
Change-Id: Ifa71ce9dddb6d0e68e09ee969d217d1514105a1a
Reviewed-on: https://review.typo3.org/56006


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>