UdpSocketState.processRecvCompletion

Process a completed receive operation.

Called when an overlapped receive has completed. Retrieves the result, delivers data to the callback, and submits the next receive if the socket is still bound and not paused.

When receiving is paused, datagrams are buffered in _pausedReceiveQueue instead of being delivered immediately. The buffered datagrams will be delivered when resumeReceiving() is called.