[Dual Shade] Show single shade on phones in landscape orientation.

Prior to this change, a narrow device (phone) in landscape orientation
would show either split shade (if dual shade is disabled) or dual shade
(if enabled).

This would cause the effect that when the user opted out of dual shade,
they would see split shade when rotating the phone to landscape. Once we
get rid of split shade this would be dual shade, also a surprising
behavior for the user. The single shade UI is preferred in this state.

Fix: 433709856
Test: Tested manually by rotating a phone with single shade, and
 observing that single shade is shown in landscape orientation as well.
Test: Added and updated unit tests.
Flag: com.android.systemui.scene_container
Change-Id: Ia34dc03a2845c03e3600d631e5699fec87001100