Make drag window a trusted overlay

We added new functionality to pilferPointers API in ag/18234604.
Using it we can extend the functionality of drag and drop to
allow user to interact with the UI while using 1 pointer/finger
to drag.
DD: go/global_drag_and_drop

Bug: 220109830

Test: atest inputflinger_tests
Change-Id: Ieb890ce71c938b4f8c6b0256fe14887b9e3968d1