WASI state serialization doesn't preserve unread stdin bytes

[MarkMcCaskey]

When serializing WASI state we ignore unread stdin bytes.

Maybe this is the correct behavior? This needs design and more thought before we can fix it.

See #726 for more context

[Hywan]

I believe it is the correct and expected behavior. Serializing is not used to “pause” the runtime in this context, but rather to “save” the compiled module, to later re-instantiating it quickly. Keeping the stdin bytes would be a terrible behavior in this context because the execution context would be totally different. I'm closing this issue :-).