Move drag event to InputDispatcher (4/n)

Currently, any window or windowless surface could receive drag event if
it is visible and touch-deliverable. But it's hard to tell if a surface
could receive this drag event in WM side because we didn't know the
final touch region of the surface that could be cropped by others.

- add isDragDrop to transferTouchFocus, true when called from drag/drop.
- ACTION_DRAG_EXITED/ACTION_DRAG_LOCATION will be sent from
  InputDispatcher to InputEventReceiver.

Bug: 158242495
Test: atest CrossAppDragAndDropTests DragDropTest
Test: atest WmTests:DragDropControllerTests

Change-Id: I111b6dbb6826fc77749fa2250ff4daced98979d2