Ambient wallpaper API feedback

Making this api a @SystemApi, protecting it with a permission and
changing boolean animation parameter to a long.

Change-Id: Ife6aac2806a5590288a801751f22d85c3cfd4622
Fixes: 116117810
Test: atest DozeWallpaperStateTest
Test: atest WallpaperServiceTest
Test: set image wallpaper
Test: set AOD wallpaper that holds permission
Test: set AOD wallpaper that doesn't hold permission