Add support for live wallpapers in theme bundles

Allow theme bundles to specify a component name
corresponding to a live wallpaper (which must exist in
the device) instead of a drawable asset.
Also update the usage of WallpaperSetter for the case
of LiveWallpaper.

Bug: 130734277
Change-Id: Ie37dcb391515c5b080884bbdfc794f80ee73cdf8