For fixed rotation test assert that PiP is within screen bounds

This is done by asserting on the center point of the PiP window, since
in the fixed rotation case the full PiP bounds can temporarily go
outside of screen bounds, as it is resizing from landscape fullscreen
to final PiP size.

The transition also involves rotating the display, which is why we have
to first assert against starting bounds in landscape, and then check
against the portrait bounds at the end of the transition. At that point
we are asserting full PiP bounds though, as it is expected to be fully
inside the display bounds.

Test: atest EnterPipToOtherOrientation
Bug: 275092905
Flag: none

Change-Id: I87f42c9c96e5a01c8aff44c6c44a06fb9d29c2de