Add automated tests to verify the validity of generated `.wat` files

[tanishiking]

Currently, our testing focuses on the generated .wasm files, while the .wat files are primarily for debugging purposes. We utilize these .wat files for browsing or verifying validity by passing them through the wasm reference interpreter (for instance, using https://github.com/tanishiking/wasmgc-docker).

Although these .wat files are primarily intended for development, they should be to, at least, ensure their validity through CI by passing through to the wasm reference interpreter.