[BUGFIX] Prevent drop down menus in docheader from being cut off

Drop down menus, used in the docheader (e.g. the
language selection in then page module) do no longer
get cut off on small screens.

This is done by setting a dynamic max-height
(viewport height - topbar and docheader height)
and by allowing to scroll.

Resolves: #103074
Releases: main, 12.4
Change-Id: Icd5f6d9c245f40c55e47e1f18901467a5703bc16
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83037


Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>