Rewrite the core

[torch2424]

There have been a TON of improvements to AssemblyScript, and tons of optimizations done to the runtime. And now with as-bind as well, the core could be greatly simplified and much more maintainable, and would probably get a speed boost in my opinion.

I think this should happen after the pixel fifo branch is merged: https://github.com/torch2424/wasmboy/tree/graphics-rewrite-pixel-fifo