wamr: Generate libc binding from NuttX

[no1wudi]

Summary

Bypass libc and other system calls into NuttX directly, similar to WAMR's builtin libc but cover more interface, must works with --bounds-checks=0 now, so it's more like an alternative to ELF (with addition XIP support from WAMR).

Compared to ELF, this solution has better footprint (don't need to load entire ELF into RAM), and can take safety feature from Wasm in future (support boundary checks).

Impact

New feature

Testing

Vela