Add sockets streams suite

[jasnell]

More test consolidations.

[ask-bonk]

The greet peer has already sent EOF before reader.cancel() runs, so this passes if cancellation is a no-op; socket.close() then supplies the observed closure. Keep the peer open, cancel an actually pending read, and observe the public closed promise.

Suggested change

	const socket = connect(greetAddress(env));
	const reader = socket.readable.getReader();
	await reader.read(); // take the greeting (or its first fragment)
	await reader.cancel('done');
	await socket.close();
	ok(true);
	async test(ctrl, env) {
	const socket = connect(echoAddress(env));
	await socket.opened;
	const reader = socket.readable.getReader();
	const pendingRead = reader.read();
	await reader.cancel('done');
	await pendingRead;
	await socket.close();
	await socket.closed;
	},

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

Adds a dual-implementation socket-streams test suite with TCP echo sidecars.

1. Medium cancelReadableSettlesSocket does not exercise cancellation of a live read. Posted one inline suggestion to correct it.

Verification could not complete: Bazel lacks libc++ headers in this runner.

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