Fix issue #3420898: More wallpaper issues

- The ImageWallpaper wasn't watching for the desired dimensions to
  change, at which point it needs to resize its surface.
- The system process has been running with the small dalvik heap
  limit, which is too tight with these huge wallpapers; this would
  cause switching wallpapers to eventually stop working as it
  couldn't get the memory it needed to load the new one.
- The compatibility mode background surface had a bunch of issues,
  such as moving its windows to the right by the window size to
  make them disappear.  This of course doesn't play well with the
  now super-sized wallpaper surface.  This code is re-worked to
  not require such shenanigans.

Change-Id: I64fde4059645d8507f1c4761ba6c17b89877a5c0