RtpTransceiver bindings & requirements for publishing tracks (#39)

- RtpSender
- RtpReceiver
- RtpTransceiver
- RtpParameters
- VideoFrameBuilder
- Interior mutability on c++ side
- Cleanup bindings ( Use #pragma once instead of include guards )
     - webrtc-sys/src/* headers are now used in only one place 
     - Avoid confusion between generated headers and our headers
- AdaptedVideoTrackSource
- Cleanup the workaround with unsupported Vec<Shared<T>>
    - Put everything inside one file

webrtc-sys/include/livekit/peer_connection_factory.h

@@ -2,18 +2,22 @@
 // Created by Théo Monnom on 03/08/2022.
 //
 
-#ifndef PEER_CONNECTION_FACTORY_H
-#define PEER_CONNECTION_FACTORY_H
+#pragma once
 
 #include "api/peer_connection_interface.h"
 #include "peer_connection.h"
-#include "rust_types.h"
 #include "webrtc.h"
 
 namespace livekit {
 using NativeRTCConfiguration =
     webrtc::PeerConnectionInterface::RTCConfiguration;
 
+class PeerConnectionFactory;
+}  // namespace livekit
+#include "webrtc-sys/src/peer_connection_factory.rs.h"
+
+namespace livekit {
+
 class PeerConnectionFactory {
  public:
   explicit PeerConnectionFactory(std::shared_ptr<RTCRuntime> rtc_runtime);
@@ -33,5 +37,3 @@ std::unique_ptr<PeerConnectionFactory> create_peer_connection_factory(
 std::unique_ptr<NativeRTCConfiguration> create_rtc_configuration(
     RTCConfiguration conf);
 }  // namespace livekit
-
-#endif  // PEER_CONNECTION_FACTORY_H