Support wasm32-wasi-threads

[toyobayashi]

build with wasi-sdk-20.0+threads, missing multithreaded libc++.a so node-addon-api is unavailable in this pre-release version of wasi-sdk.

[toyobayashi]

Locally tested node-addon-api with https://github.com/WebAssembly/wasi-sdk/actions/runs/4266056953#artifacts.

[toyobayashi]

async work / tsfn may throw error in browser main thread due to pthread API use __builtin_wasm_memory_atomic_wait32 internally.

Approach:

• User choose a Worker thread as emnapi main thread (like StackBlitz runs Node.js code in seperate Web Workers)
• Emnapi provide another async work and tsfn implementation written in pure JavaScript (need further investigation)
• Modify wasi-libc's futex_wait with busy wait in browser main thread (less feasible)