[TASK] Apply dark style to module menu scrollbar

The default light system-ui scrollbars are very distracting on
the dark module menu surface. Therefore they are now replaced
by a more appealing dark-mode scrollbar style, as provided
by the browser vendor.

Resolves: #95047
Releases: main, 11.5
Change-Id: Iecba9635118f4dc4ba612b286abe4562b53c5b75
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74255


Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>