chore: Add simulate for candidate protocol switch. (#176)

example/lib/exts.dart

@@ -174,5 +174,6 @@ enum SimulateScenarioResult {
   nodeFailure,
   migration,
   serverLeave,
+  switchCandidate,
   clear,
 }

example/lib/widgets/controls.dart

@@ -222,6 +222,8 @@ class _ControlsWidgetState extends State<ControlsWidget> {
         nodeFailure: result == SimulateScenarioResult.nodeFailure ? true : null,
         migration: result == SimulateScenarioResult.migration ? true : null,
         serverLeave: result == SimulateScenarioResult.serverLeave ? true : null,
+        switchCandidate:
+            result == SimulateScenarioResult.switchCandidate ? true : null,
       );
     }
   }

lib/src/core/room.dart

@@ -575,12 +575,14 @@ extension RoomDebugMethods on Room {
     bool? nodeFailure,
     bool? migration,
     bool? serverLeave,
+    bool? switchCandidate,
   }) async {
     engine.signalClient.sendSimulateScenario(
       speakerUpdate: speakerUpdate,
       nodeFailure: nodeFailure,
       migration: migration,
       serverLeave: serverLeave,
+      switchCandidate: switchCandidate,
     );
   }
 }

lib/src/core/signal_client.dart

@@ -438,6 +438,7 @@ extension SignalClientRequests on SignalClient {
     bool? nodeFailure,
     bool? migration,
     bool? serverLeave,
+    bool? switchCandidate,
   }) =>
       _sendRequest(lk_rtc.SignalRequest(
         simulate: lk_rtc.SimulateScenario(
@@ -445,6 +446,9 @@ extension SignalClientRequests on SignalClient {
           nodeFailure: nodeFailure,
           migration: migration,
           serverLeave: serverLeave,
+          switchCandidateProtocol: (switchCandidate != null && switchCandidate)
+              ? lk_rtc.CandidateProtocol.TCP
+              : null,
         ),
       ));
 }