Add E2E test for test case display empty view for favorite folder

integration_test/tests/mailbox/display_empty_view_for_favorite_folder_test.dart

@@ -0,0 +1,9 @@
+import '../../base/test_base.dart';
+import '../../scenarios/mailbox/display_empty_view_for_favorite_folder_scenario.dart';
+
+void main() {
+  TestBase().runPatrolTest(
+    description: 'Should display empty view when no mail favorites',
+    scenarioBuilder: ($) => DisplayEmptyViewForFavoriteFolderScenario($),
+  );
+}