Add pointerType to NestedDraggable.onDragStarted()

This CL adds the type of the first pointer that was down when a drag is
detected. This will be used to be able to specify different actions
depending on the pointer type.

Bug: 378470603
Test: atest NestedDraggableTest
Flag: EXEMPT NestedDraggable is not used yet
Change-Id: I9af3f5eb4196f728e5da8bd9bca3718643c39e5a