[in_app_purchase] Activate leak testing for android (#8369)

The android package manipulates disposable objects. This PR activate leak testing to make sure disposable objects are correctly disposed.

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

Author: ValentinVignal

packages/in_app_purchase/in_app_purchase_android/pubspec.yaml

@@ -26,6 +26,7 @@ dev_dependencies:
   build_runner: ^2.0.0
   flutter_test:
     sdk: flutter
+  leak_tracker_flutter_testing: any
   mockito: ^5.4.4
   pigeon: ^22.4.2
   test: ^1.16.0

packages/in_app_purchase/in_app_purchase_android/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();
+}