wasi-io: Missing would-block in stream-error (Returning 0 from TcpReader::read)

[Heap-Hop]

wasmtime/crates/wasi/src/tcp.rs

Lines 719 to 723 in 6767488

	// Failing with `EWOULDBLOCK` is how we differentiate between a closed channel and no
	// data to read right now.
	Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => 0,

Returning 0 for std::io::ErrorKind::WouldBlock causes downstream to interpret it as a closed stream, see:
yoshuawuyts/wstd#25 (comment).
https://github.com/yoshuawuyts/wstd/blob/5ce367add5e7bcb569b6487453cb9ba94468dc99/src/io/copy.rs#L12

This is also found in:

wasmtime/crates/test-programs/src/bin/preview2_tcp_streams.rs

Lines 17 to 22 in 6767488

	// The input stream should immediately signal StreamError::Closed.
	// Notably, it should _not_ return an empty list (the wasi-io equivalent of EWOULDBLOCK)
	// See: https://github.com/bytecodealliance/wasmtime/pull/8968
	assert!(matches!(client.input.read(10), Err(StreamError::Closed)));

Given that the wit files already include many would-block errors, would it make sense to extend stream-error to include a would-block?