Log undecryptable to-device events

Listen for the new undecryptable to-device event event and log
events for it in Posthog & Sentry, and make it visible in the
call flow diagram.

src/PosthogEvents.ts

@@ -149,3 +149,17 @@ export class MuteCameraTracker {
     });
   }
 }
+
+interface UndecryptableToDeviceEvent {
+  eventName: "UndecryptableToDeviceEvent";
+  callId: string;
+}
+
+export class UndecryptableToDeviceEventTracker {
+  track(callId: string) {
+    PosthogAnalytics.instance.trackEvent<UndecryptableToDeviceEvent>({
+      eventName: "UndecryptableToDeviceEvent",
+      callId,
+    });
+  }
+}