ChatControlBase: Add support for KDE notification drag and drop

This adds Gdk.DragAction.MOVE to the drag_dest, enabling Gajim to process
dropped items from KDE notifications (for example). Fixes #9011
3 jobs for drop-kde-notification in 3 minutes and 2 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed run-appdata #17894

00:00:05

passed run-tests #17893

00:02:49

 
  Build
passed run-build #17895

00:00:08