[WIP] WASM lod tracker

[avaer]

This moves the logic of https://github.com/webaverse/app/blob/master/lod.js to WASM, since it was a performance problem.

The issue isn't so much that this code is heavy, but that it happens a lot (at least once for every terrain layer), and it happens at asynchronous times while also causing GC stops, which causes frame timing jitter.

When we ship this:

• merge all lod-requesting apps into one tracker (will give us 5x perf boost)
• cancel all data requests before issuing a lod swap (smoother GC behavior since we can forget it earlier)
• have a minimum binding for DataRequest/Dominiator listen on the JS side so it does not interfere with frame timing