Adding deviceId to KeyEventChannel enconding method (#12958)

This Pull Request simple adds the deviceId property to the encoding method, I am preparing a next PR on the flutter repository that reads this info and add a property to RawKeyEventDataAndroid on the Flutter side.

This is necessary so we can support multiple gamepads on Android, in order to be possible to make a local multiplayer game with Flutter.

Author: erickzanardo

shell/platform/android/io/flutter/embedding/engine/systemchannels/KeyEventChannel.java

@@ -60,6 +60,7 @@ private void encodeKeyEvent(@NonNull FlutterKeyEvent event, @NonNull Map<String,
     message.put("source", event.source);
     message.put("vendorId", event.vendorId);
     message.put("productId", event.productId);
+    message.put("deviceId", event.deviceId);
   }
 
   /**