Instead of going into an unnecessary animation loop, we can simply wait to be notified when tiles load.
The WebGL renderer still sets frameState.animate true, but I think this too should be unnecessary (full page example works without it, side-by-side example shows it cannot yet be removed).
Instead of keeping track of wanted tile ranges, we can instead track wanted tiles individually. This provides enough for the map to know how to prioritize tiles and should be more efficient (no extra calls to extend tile ranges or check for tile containment within a range).
