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_publication.dart

@@ -1,4 +1,4 @@
-import '../proto/livekit_models.pb.dart';
+import '../proto/livekit_models.pb.dart' as lk_models;
 import 'track.dart';
 
 /// Represents a track that's published to the server. This class contains
@@ -7,14 +7,14 @@ class TrackPublication {
   Track? track;
   String name;
   String sid;
-  TrackType kind;
+  lk_models.TrackType kind;
   bool muted = false;
   bool simulcasted = false;
   TrackDimension? dimension;
 
   bool get subscribed => track != null;
 
-  TrackPublication.fromInfo(TrackInfo info)
+  TrackPublication.fromInfo(lk_models.TrackInfo info)
       : sid = info.sid,
         name = info.name,
         kind = info.type {
@@ -22,12 +22,12 @@ class TrackPublication {
   }
 
   /// True when the track is published with name [Track.screenShareName].
-  bool get isScreenShare => kind == TrackType.VIDEO && name == Track.screenShareName;
+  bool get isScreenShare => kind == lk_models.TrackType.VIDEO && name == Track.screenShareName;
 
-  void updateFromInfo(TrackInfo info) {
+  void updateFromInfo(lk_models.TrackInfo info) {
     muted = info.muted;
     simulcasted = info.simulcast;
-    if (info.type == TrackType.VIDEO) {
+    if (info.type == lk_models.TrackType.VIDEO) {
       dimension = TrackDimension(info.width, info.height);
     }
   }