New user settings for ambient aod wallpapers

On supported devices, allow the user to turn ambient
wallpapers on/off, defaulting to on.

Test: atest WallpaperRepositoryImplTest
Flag: com.android.systemui.shared.ambient_aod
Bug: 373844670

Change-Id: Ie8bf6c92bdcdc037fa890c970988b8b7aa3c256f