Fix CTS tests AnimationEdgeExtensionTests by relying on proper Insets

The current test relied on certain window names (and that there is only
one for insets).

Now we fix that by using the proper insets functionality of the Android
windowing system.

Test: These tests pass (though they are a little flakey depending on screenshot time)
Bug: 226699695
Change-Id: Iad45a75b263da617ecdc57bb7d08e910d0f13a1c
2 files changed