Add APIs for setting static wallpaers using WallpaperDescription

These APIs are not being called yet, but are being added now to be part
of the 25Q2 API bump.

Bug: 380244842
Flag: android.app.live_wallpaper_content_handling
Test: tests included with new code
Change-Id: I8af4f4417619c81e37469f2f2adbd4471e1328df