[TASK] Rework Module-Menu CSS/Less

Overwork Module-Menu CSS without visual changes.

Resolves: #62161
Releases: master
Change-Id: I8670548c7192d337550589d4aa325a63d186b1c3
Reviewed-on: http://review.typo3.org/33261
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>