when call RTCRtpTransceiver's set_direction, Update the negotiation-needed flag for connection #51
Description
https://github.com/webrtc-rs/rtc/blob/master/rtc/src/rtp_transceiver/internal.rs#L159
//TODO: https://www.w3.org/TR/webrtc/#dom-rtcrtptransceiver-direction
// Update the negotiation-needed flag for connection.