Support ambient aod wallpaper on foldables

Only some displays may support this, so allow an override that
systemui can use while still specifying general device support.

Fixes: 414284526
Test: atest WallpaperRepositoryImplTest
Flag: com.android.systemui.shared.ambient_aod
Change-Id: Iccef9ba747eff0c00a5f73b7fa6bd49e8aed13b9