Copy the generated JS runtime into OUT_DIR #296

The generated runtime binary is stored under target/hyperlight-js-runtime, outside OUT_DIR. Cached builds can therefore use a stale or missing runtime. This is annoying and should be fixed, I believe by copying the final binary to OUT_DIR, and include_bytes! the file in OUT_DIR instead of the external location.

Relates to hyperlight-dev/hyperlight-wasm#547