Always use display coords for unhandled drop events

- If an app starts a drag with DRAG_FLAG_GLOBAL_SAME_APPLICATION, input
  will still report the drop over a non-notified window (ie. one that
  did not receive DRAG_STARTED) with window-relative coordinates instead
  of display coordinates that Shell expects.

Fixes: 438975251
Flag: EXEMPT bugfix
Test: atest DragDropControllerTests
Change-Id: I01183596b74f62267aadba65c0c3e2b5b707783f