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/yuv_helper.h

@@ -2,12 +2,12 @@
 // Created by Théo Monnom on 01/12/2022.
 //
 
-#ifndef CLIENT_SDK_NATIVE_YUV_HELPER_H
-#define CLIENT_SDK_NATIVE_YUV_HELPER_H
+#pragma once
 
 #include <memory>
 
 #include "api/video/yuv_helper.h"
+#include "webrtc-sys/src/yuv_helper.rs.h"
 
 namespace livekit {
 
@@ -68,5 +68,3 @@ static void i420_to_rgba(const uint8_t* src_y,
 }
 
 }  // namespace livekit
-
-#endif  // CLIENT_SDK_NATIVE_YUV_HELPER_H