New Threading System

[lachlansneff]

I'm at a hackathon right now so I'm planning on dedicating a lot of time to ripping out the old threading system.

The aim is to make all processes single-threaded to reduce synchronization overhead. This should also make the interface between usercode and the kernel a lot faster and simpler.

• Remove multi-threading from processes.

• Remove dynamic dispatching from api objects.

• Somehow check api object type before calling api.

• Remove synchronization from wasm table accesses.