[core][general] Add metadata file tracking to aid in "Golden Tests" regeneration (#6325)

samples/client/petstore/dart/openapi-browser-client/.openapi-generator/FILES

@@ -0,0 +1,33 @@
+.analysis_options
+.gitignore
+.travis.yml
+README.md
+doc/ApiResponse.md
+doc/Category.md
+doc/Order.md
+doc/Pet.md
+doc/PetApi.md
+doc/StoreApi.md
+doc/Tag.md
+doc/User.md
+doc/UserApi.md
+git_push.sh
+lib/api.dart
+lib/api/pet_api.dart
+lib/api/store_api.dart
+lib/api/user_api.dart
+lib/api_client.dart
+lib/api_exception.dart
+lib/api_helper.dart
+lib/auth/api_key_auth.dart
+lib/auth/authentication.dart
+lib/auth/http_basic_auth.dart
+lib/auth/http_bearer_auth.dart
+lib/auth/oauth.dart
+lib/model/api_response.dart
+lib/model/category.dart
+lib/model/order.dart
+lib/model/pet.dart
+lib/model/tag.dart
+lib/model/user.dart
+pubspec.yaml