Such windows are typically used as mostly transparent overlays on top
of other windows underneath. Letting such an overlay become the key
window breaks cursor updates and focus handling.
Pick-to: 6.0 6.1 5.15
Fixes: QTBUG-83632
Change-Id: I192d419a5bdb8dfa0e9223e9fbbd7876c62fe743
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>