[WS] Implement wslay unbuffered message parsing

Ensure we never read more than we can store during poll.

Raise default max packets to 4096 to maintain the same performance for
the first 2048 packets.

modules/websocket/packet_buffer.h

@@ -104,6 +104,14 @@ public:
 		return _queued;
 	}
 
+	int payload_space_left() const {
+		return _payload.space_left();
+	}
+
+	int packets_space_left() const {
+		return _packets.size() - _queued;
+	}
+
 	void clear() {
 		_payload.resize(0);
 		_packets.resize(0);