Wait for test activity to be on top

In a previous CL, we added a wait for stable geometry. However, what we
actually care about is that the test activity is shown on top. In this
CL, the wait is updated to ensure that the window is on top.

Bug: 385141667
Flag: TEST_ONLY
Test: atest UinputRecordingIntegrationTests
Change-Id: I0a83f5ee4f9af0f82a383349b56db3fc4b79eef5