base1: Limit the maximum dropdown-menu height and scroll
base1: Limit the maximum dropdown-menu height and scroll

When a dropdown menu gets too large, the first option is that it
should probably be replaced by another control, such as a searchable
list.

However in places where the expansion is a corner case, or the screen
is very small we should show a scrollable menu. That's what this pull
request does.

Issue #4944
Closes #4945
Reviewed-by: Peter <a316049dd34607c62d4611d63ab22a6454add223@redhat.com>

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