Fix creating unexpected letterbox surfaces

With fixed rotation, the rotated activity should compare bounds
with rotated display. Otherwise AR#isLetterboxedAppWindow will
return false and create unnecessary letterbox surfaces.

Note that fixed rotation only applies when display area matches
display bounds.

The method matchesDisplayBounds is removed because the only usage
in WS#computeFrame uses parent frame, that is computed from
configuration bounds which doesn't tie to an actual display.

Fix: 186407859
Test: DisplayContentTests#testApplyTopFixedRotationTransform
Change-Id: I8cd978844f0ba8f9739f90c5c624d0c5fc3dc339