Untangles dependencies by splitting up `engine.{h,cpp}` into 3 files:
1. `primitive_render`
2. `ticks` -- only contains `GetAnimationFrame` for now.
3. `GetWidth2` renamed to `CalculateSpriteTileCenterX` and moved to `levels/dun_tile.hpp`.
4 options args are a bit unwieldy, especially when you want
to pass only the first and the last one.
With a struct, there is no need to specify the default values
for the args in between.