feat: video publishing (#42)

- Prepare webrtc abstraction ( for future wasm support )
- Added track publish support for videos
  - Added LogoTrack example to simple_room demo
- Lot of cleanup
- There are compiler warnings I'll solve on our v1 release

livekit-webrtc/src/native/rtp_sender.rs

@@ -0,0 +1,46 @@
+use super::media_stream::new_media_stream_track;
+use crate::{
+    media_stream::MediaStreamTrack, rtp_parameters::RtpParameters, RtcError, RtcErrorType,
+};
+use cxx::SharedPtr;
+use webrtc_sys::{rtc_error::ffi::RTCError, rtp_sender as sys_rs};
+
+#[derive(Clone)]
+pub struct RtpSender {
+    pub(crate) sys_handle: SharedPtr<sys_rs::ffi::RtpSender>,
+}
+
+impl RtpSender {
+    pub fn track(&self) -> Option<MediaStreamTrack> {
+        let track_handle = self.sys_handle.track();
+        if track_handle.is_null() {
+            return None;
+        }
+
+        Some(new_media_stream_track(track_handle))
+    }
+
+    pub fn set_track(&self, track: Option<MediaStreamTrack>) -> Result<(), RtcError> {
+        if !self
+            .sys_handle
+            .set_track(track.map_or(SharedPtr::null(), |t| t.sys_handle()))
+        {
+            return Err(RtcError {
+                error_type: RtcErrorType::InvalidState,
+                message: "Failed to set track".to_string(),
+            });
+        }
+
+        Ok(())
+    }
+
+    pub fn parameters(&self) -> RtpParameters {
+        self.sys_handle.get_parameters().into()
+    }
+
+    pub fn set_parameters(&self, parameters: RtpParameters) -> Result<(), RtcError> {
+        self.sys_handle
+            .set_parameters(parameters.into())
+            .map_err(|e| unsafe { RTCError::from(e.what()).into() })
+    }
+}