Ignore all input outside of clipboard UI

Touches outside the UI should pass through but also dismiss the UI. This
can be done with insets in the draggable constraint layout (similar to
how ScreenshotView works).

Bug: 221509682
Test: manual test of bug repro.
Change-Id: I9fab0bff52e647cbeb8cb53a18a6603bb5c4195f
1 file changed