_RouterState should dispose created _RestorableRouteInformation. (#136556)

### Description
- Fixes https://github.com/flutter/flutter/issues/134205.

### Tests
- Removes ignoring the `_RestorableRouteInformation` leak from `cupertino/app_test.dart`;
- Removes ignoring the `_RestorableRouteInformation` leak from `material/app_test.dart`;
- Removes ignoring the `_RestorableRouteInformation` leak from `widgets/app_test.dart`;
- Removes ignoring the `_RestorableRouteInformation` leak from `widgets/route_notification_messages_test.dart`;
- Removes ignoring the `_RestorableRouteInformation` leak from `widgets/router_restoration_test.dart`;
- Updates `widgets/router_test.dart` to use `testWidgetsWithLeakTracking`.

packages/flutter/lib/src/widgets/router.dart

@@ -632,6 +632,10 @@ class _RouterState<T> extends State<Router<T>> with RestorationMixin {
   }
 
   void _reportRouteInformation(Duration timestamp) {
+    if (!mounted) {
+      return;
+    }
+
     assert(_routeInformationReportingTaskScheduled);
     _routeInformationReportingTaskScheduled = false;
 
@@ -726,6 +730,7 @@ class _RouterState<T> extends State<Router<T>> with RestorationMixin {
 
   @override
   void dispose() {
+    _routeInformation.dispose();
     widget.routeInformationProvider?.removeListener(_handleRouteInformationProviderNotification);
     widget.backButtonDispatcher?.removeCallback(_handleBackButtonDispatcherNotification);
     widget.routerDelegate.removeListener(_handleRouterDelegateNotification);

packages/flutter/test/cupertino/app_test.dart

@@ -178,12 +178,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  // TODO(polina-c): remove after fixing
-  // https://github.com/flutter/flutter/issues/134205
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    allowAllNotDisposed: true,
-  ));
+  });
 
   testWidgetsWithLeakTracking('CupertinoApp.router route information parser is optional', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -209,12 +204,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  // TODO(polina-c): remove after fixing
-  // https://github.com/flutter/flutter/issues/134205
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    allowAllNotDisposed: true,
-  ));
+  });
 
   testWidgetsWithLeakTracking('CupertinoApp.router throw if route information provider is provided but no route information parser', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -300,12 +290,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  // TODO(polina-c): remove after fixing
-  // https://github.com/flutter/flutter/issues/134205
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    allowAllNotDisposed: true,
-  ));
+  });
 
   testWidgetsWithLeakTracking('CupertinoApp has correct default ScrollBehavior', (WidgetTester tester) async {
     late BuildContext capturedContext;

packages/flutter/test/material/app_test.dart

@@ -1114,12 +1114,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  // TODO(polina-c): remove after fixing
-  // https://github.com/flutter/flutter/issues/134205
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    allowAllNotDisposed: true,
-  ));
+  });
 
   testWidgetsWithLeakTracking('MaterialApp.router route information parser is optional', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -1145,12 +1140,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  // TODO(polina-c): remove after fixing
-  // https://github.com/flutter/flutter/issues/134205
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    allowAllNotDisposed: true,
-  ));
+  });
 
   testWidgetsWithLeakTracking('MaterialApp.router throw if route information provider is provided but no route information parser', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -1236,12 +1226,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  // TODO(polina-c): remove after fixing
-  // https://github.com/flutter/flutter/issues/134205
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    allowAllNotDisposed: true,
-  ));
+  });
 
   testWidgetsWithLeakTracking('MaterialApp.builder can build app without a Navigator', (WidgetTester tester) async {
     Widget? builderChild;

packages/flutter/test/widgets/app_test.dart

@@ -304,12 +304,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    // TODO(ksokolovskyi): remove after fixing
-    // https://github.com/flutter/flutter/issues/134205
-    notDisposedAllowList: <String, int?> {'_RestorableRouteInformation': 1},
-  ));
+  });
 
   testWidgetsWithLeakTracking('WidgetsApp.router route information parser is optional', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -336,12 +331,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    // TODO(ksokolovskyi): remove after fixing
-    // https://github.com/flutter/flutter/issues/134205
-    notDisposedAllowList: <String, int?> {'_RestorableRouteInformation': 1},
-  ));
+  });
 
   testWidgetsWithLeakTracking('WidgetsApp.router throw if route information provider is provided but no route information parser', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -432,12 +422,7 @@ void main() {
     await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
-  },
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    // TODO(ksokolovskyi): remove after fixing
-    // https://github.com/flutter/flutter/issues/134205
-    notDisposedAllowList: <String, int?> {'_RestorableRouteInformation': 1},
-  ));
+  });
 
   testWidgetsWithLeakTracking('WidgetsApp.router has correct default', (WidgetTester tester) async {
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
@@ -453,12 +438,7 @@ void main() {
       color: const Color(0xFF123456),
     ));
     expect(find.text('/'), findsOneWidget);
-  },
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    // TODO(ksokolovskyi): remove after fixing
-    // https://github.com/flutter/flutter/issues/134205
-    notDisposedAllowList: <String, int?> {'_RestorableRouteInformation': 1},
-  ));
+  });
 
   testWidgetsWithLeakTracking('WidgetsApp has correct default ScrollBehavior', (WidgetTester tester) async {
     late BuildContext capturedContext;

packages/flutter/test/widgets/route_notification_messages_test.dart

@@ -316,12 +316,7 @@ void main() {
         'replace': false,
       }),
     ]);
-  },
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    // TODO(ksokolovskyi): remove after fixing
-    // https://github.com/flutter/flutter/issues/134205
-    notDisposedAllowList: <String, int?> {'_RestorableRouteInformation': 1},
-  ));
+  });
 }
 
 typedef SimpleRouterDelegateBuilder = Widget Function(BuildContext, RouteInformation);

packages/flutter/test/widgets/router_restoration_test.dart

@@ -40,12 +40,7 @@ void main() {
     expect(find.text('Current config: /foo'), findsOneWidget);
     expect(delegate().newRoutePaths, isEmpty);
     expect(delegate().restoredRoutePaths, <String>['/foo', '/foo']);
-  },
-  leakTrackingTestConfig: const LeakTrackingTestConfig(
-    // TODO(ksokolovskyi): remove after fixing
-    // https://github.com/flutter/flutter/issues/134205
-    notDisposedAllowList: <String, int?> {'_RestorableRouteInformation': 2},
-  ));
+  });
 
   testWidgets('Router state restoration with RouteInformationProvider', (WidgetTester tester) async {
     final UniqueKey router = UniqueKey();