[google_maps_flutter] Activate leak testing (#8368)

Activate leak testing for google_maps_flutter. The package uses disposable objects, it will make sure those are properly disposed.  

See the documentation: https://github.com/dart-lang/leak_tracker/blob/main/doc%2Fleak_tracking%2FDETECT.md

packages/google_maps_flutter/google_maps_flutter/pubspec.yaml

@@ -29,6 +29,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  leak_tracker_flutter_testing: any
   plugin_platform_interface: ^2.1.7
   stream_transform: ^2.0.0
 

packages/google_maps_flutter/google_maps_flutter/test/flutter_test_config.dart

@@ -0,0 +1,13 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
+
+Future<void> testExecutable(FutureOr<void> Function() testMain) async {
+  LeakTesting.enable();
+  LeakTracking.warnForUnsupportedPlatforms = false;
+  await testMain();
+}