Simulcast, Screen sharing & Various improvements (#4)

* Respect `RTCIceTransportPolicy` enum and organize

* Simplify syntax where possible etc.

* Combine `VideoPreset` and `VideoPresets`

* Default values for `ConnectOptions`

* Build URI instead of String manipulation

* Slight modifications to Exception

* `LiveKitTheme` for example

* `VideoEncoding` class

* Organize imports

* First simulcast implementation

* Remove unnecessary try-catches

* Update Android settings

* Remember uri and token

* example improvements

* `fit` parameter for VideoTrackRenderer

* Simulcast option for example

* Pass `defaultPublishOptions`

* Show only `VideoQuality`

* Pass tests

* Better buildUri logic

* Named parameter to positional

* Explicit imports

* `VideoParameter` instead of `VideoPreset`

* Use `mediaTrack.getSettings` when possible

* Safer dispose logic

* Safer `PCTransport`

Update transport.dart

* Synchronized events for `SignalClient`

* Use logger instead of print

* Make example compile for iOS

* First screen share implementation

* Make example work with screen share

* Example improvement

* Code optimization

* Don't depend on web_socket_channel

* Fix: Unpublish track bug

* Show participant mute state & identity

* Update protos

* Remote mute/unmute

* iOS Background mode

* Separate `createCameraTrack` and `createScreenTrack`

* Clean up

* PB fix

* format

* Fix analyzer warning

* Android clean up

* Update README.md

* Clean up

lib/src/track/track.dart

@@ -1,7 +1,7 @@
 import 'package:flutter_webrtc/flutter_webrtc.dart';
 import 'package:uuid/uuid.dart';
 
-import '../proto/livekit_models.pb.dart';
+import '../proto/livekit_models.pb.dart' as lk_models;
 
 class TrackDimension {
   int width;
@@ -12,24 +12,25 @@ class TrackDimension {
 
 /// Wrapper around a MediaStreamTrack with additional metadata.
 class Track {
+  static const cameraName = 'camera';
   static const screenShareName = 'screen';
 
   String name;
-  TrackType kind;
-  MediaStreamTrack mediaTrack;
+  lk_models.TrackType kind;
+  MediaStreamTrack mediaStreamTrack;
   String? sid;
   RTCRtpTransceiver? transceiver;
   String? _cid;
 
-  Track(this.kind, this.name, this.mediaTrack);
+  Track(this.kind, this.name, this.mediaStreamTrack);
 
-  bool get muted => mediaTrack.muted == null ? false : mediaTrack.muted!;
+  bool get muted => mediaStreamTrack.muted == null ? false : mediaStreamTrack.muted!;
 
   RTCRtpMediaType get mediaType {
     switch (kind) {
-      case TrackType.AUDIO:
+      case lk_models.TrackType.AUDIO:
         return RTCRtpMediaType.RTCRtpMediaTypeAudio;
-      case TrackType.VIDEO:
+      case lk_models.TrackType.VIDEO:
         return RTCRtpMediaType.RTCRtpMediaTypeVideo;
       // this should never happen
       default:
@@ -38,7 +39,7 @@ class Track {
   }
 
   String getCid() {
-    var cid = _cid ?? mediaTrack.id;
+    var cid = _cid ?? mediaStreamTrack.id;
 
     if (cid == null) {
       const uuid = Uuid();
@@ -48,7 +49,7 @@ class Track {
     return cid;
   }
 
-  void stop() {
-    mediaTrack.stop();
+  Future<void> stop() async {
+    await mediaStreamTrack.stop();
   }
 }