Add test for media_query_data.system_gesture_insets.0.dart (#157854)

Contributes to https://github.com/flutter/flutter/issues/130459

It adds a test for
- `examples/api/lib/widgets/media_query/media_query_data.system_gesture_insets.0.dart`

examples/api/test/widgets/media_query/media_query_data.system_gesture_insets.0_test.dart

@@ -0,0 +1,23 @@
+// Copyright 2014 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 'package:flutter/material.dart';
+import 'package:flutter_api_samples/widgets/media_query/media_query_data.system_gesture_insets.0.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('The slider should be padded with the system gesture insets', (WidgetTester tester) async {
+    tester.view.systemGestureInsets = const FakeViewPadding(left: 60, right: 60);
+    await tester.pumpWidget(
+      const example.SystemGestureInsetsExampleApp(),
+    );
+
+    expect(find.widgetWithText(AppBar, 'Pad Slider to avoid systemGestureInsets'), findsOne);
+
+    final Rect rect = tester.getRect(find.byType(Slider));
+
+    expect(rect, rectMoreOrLessEquals(const Rect.fromLTRB(20.0, 56.0, 780.0, 600.0)));
+  });
+}