[CLEANUP] Use fully-qualified class names for @param, @return and @var

This makes the code more readable.

Change-Id: I137e2951a51966ff5157f21c2fd860f039c312d3
Resolves: #58277
Releases: 6.2
Reviewed-on: https://review.typo3.org/29704
Reviewed-by: Nico de Haen
Tested-by: Nico de Haen