Support Languages through RISC-V Emulation

[rameshvarun]

Right now, we only support languages where the compiler/interpreter itself can run in WASM. For many languages, this will never be well supported (even if it's possible to hack it together).

We can support a wider variety of languages by emulating a RISC-V, linux-based machine. This should work particularly well for C, C++, and Rust, and allow code to use I/O, threading, and more that wouldn't be possible in pure WASM.

To keep machine images small, we should create minimal linux images using buildroot/busybox.

Example: https://bellard.org/jslinux/vm.html?cpu=riscv64&url=buildroot-riscv64.cfg&mem=256

x86 emulation could also be used (example: https://supabase.com/blog/postgres-wasm), but due to the complexity of the ISA, most x86 emulators only emulate a portion of the spec.