Rewrite `tcp_echo_server` test to shell out to wasmtime

[pchickey]

Right now the tentpole for CI times is building all of wasmtime for use in test-programs/artifacts/tests/tcp_echo_server.rs, which was written before we were using cargo test --target wasm32-wasip2, which uses an installed wasmtime-cli. The use of wasmtime in that file is equivelant to wasmtime run -Shttp so it should be pretty easy to swap out.

While its being rewriten that test would benefit from using tokio instead of std and threads, I was trying to write it all in terms of std "because you can" but its, surprise surprise, the exact sort of code that really benefits from being written with async rust.