wip/runtime2: Lights and cameras should never get selected over drag widget when two are overlapping

wip/runtime2:

Lights and cameras should never get selected over drag widget when two are overlapping.

Move a cube in perspective view so that head one of it's drag arrows overlaps the light indicator. Click on the drag arrow. Often, the light gets selected instead of the drag arrow, probably depending on the relative depth. The drag widgets of the currently selected object should always be preferred over the light/camera visual aid widget in picking.