[TASK] Cleanup EXT:workspaces

* Update phpDoc where needed
* Import use statements where possible
* Make use of use statements if they are there already

Resolves: #59789
Releases: 6.3
Change-Id: I2c7baa6ac9b3a085b3fed83da559fddfdbf4c950
Reviewed-on: https://review.typo3.org/31009
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters