Update menu examples for `SafeArea` (#132390)

fixes [Some of the menu examples don't contain `SafeArea`](https://github.com/flutter/flutter/issues/132388)

### Description

This fixes the menu examples for running on mobile with a safe area.

![Group 2](https://github.com/flutter/flutter/assets/48603081/0d460c00-60f5-45e0-87ee-c010ede9ee42)

examples/api/lib/material/menu_anchor/checkbox_menu_button.0.dart

@@ -101,8 +101,9 @@ class MenuApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return const MaterialApp(
-      home: Scaffold(body: MyCheckboxMenu(message: kMessage)),
+    return MaterialApp(
+      theme: ThemeData(useMaterial3: true),
+      home: const Scaffold(body: SafeArea(child: MyCheckboxMenu(message: kMessage))),
     );
   }
 }

examples/api/lib/material/menu_anchor/menu_accelerator_label.0.dart

@@ -110,7 +110,7 @@ class MenuAcceleratorApp extends StatelessWidget {
             debugDumpApp();
           }),
         },
-        child: const Scaffold(body: MyMenuBar()),
+        child: const Scaffold(body: SafeArea(child: MyMenuBar())),
       ),
     );
   }

examples/api/lib/material/menu_anchor/menu_anchor.0.dart

@@ -204,7 +204,7 @@ class MenuApp extends StatelessWidget {
   Widget build(BuildContext context) {
     return MaterialApp(
       theme: ThemeData(useMaterial3: true),
-      home: const Scaffold(body: MyCascadingMenu(message: kMessage)),
+      home: const Scaffold(body: SafeArea(child: MyCascadingMenu(message: kMessage))),
     );
   }
 }

examples/api/lib/material/menu_anchor/menu_bar.0.dart

@@ -230,7 +230,7 @@ class MenuBarApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return const MaterialApp(
-      home: Scaffold(body: MyMenuBar(message: kMessage)),
+      home: Scaffold(body: SafeArea(child: MyMenuBar(message: kMessage))),
     );
   }
 }

examples/api/lib/material/menu_anchor/radio_menu_button.0.dart

@@ -107,8 +107,9 @@ class MenuApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return const MaterialApp(
-      home: Scaffold(body: MyRadioMenu()),
+    return MaterialApp(
+      theme: ThemeData(useMaterial3: true),
+      home: const Scaffold(body: SafeArea(child: MyRadioMenu())),
     );
   }
 }

examples/api/test/material/menu_anchor/checkbox_menu_button.0_test.dart

@@ -24,4 +24,18 @@ void main() {
     expect(find.text('Show Message'), findsNothing);
     expect(find.text(example.MenuApp.kMessage), findsOneWidget);
   });
+
+  testWidgets('MenuAnchor is wrapped in a SafeArea', (WidgetTester tester) async {
+    const double safeAreaPadding = 100.0;
+    await tester.pumpWidget(
+      const MediaQuery(
+        data: MediaQueryData(
+          padding: EdgeInsets.symmetric(vertical: safeAreaPadding),
+        ),
+        child: example.MenuApp(),
+      ),
+    );
+
+    expect(tester.getTopLeft(find.byType(MenuAnchor)), const Offset(0.0, safeAreaPadding));
+  });
 }

examples/api/test/material/menu_anchor/menu_accelerator_label.0_test.dart

@@ -51,4 +51,18 @@ void main() {
     await tester.pumpAndSettle();
     expect(find.text('Close'), findsNothing);
   });
+
+  testWidgets('MenuBar is wrapped in a SafeArea', (WidgetTester tester) async {
+    const double safeAreaPadding = 100.0;
+    await tester.pumpWidget(
+      const MediaQuery(
+        data: MediaQueryData(
+          padding: EdgeInsets.symmetric(vertical: safeAreaPadding),
+        ),
+        child: example.MenuAcceleratorApp(),
+      ),
+    );
+
+    expect(tester.getTopLeft(find.byType(MenuBar)), const Offset(0.0, safeAreaPadding));
+  });
 }

examples/api/test/material/menu_anchor/menu_anchor.0_test.dart

@@ -104,4 +104,18 @@ void main() {
 
     expect(find.text('Last Selected: ${example.MenuEntry.colorBlue.label}'), findsOneWidget);
   });
+
+  testWidgets('MenuAnchor is wrapped in a SafeArea', (WidgetTester tester) async {
+    const double safeAreaPadding = 100.0;
+    await tester.pumpWidget(
+      const MediaQuery(
+        data: MediaQueryData(
+          padding: EdgeInsets.symmetric(vertical: safeAreaPadding),
+        ),
+        child: example.MenuApp(),
+      ),
+    );
+
+    expect(tester.getTopLeft(find.byType(MenuAnchor)), const Offset(0.0, safeAreaPadding));
+  });
 }

examples/api/test/material/menu_anchor/menu_bar.0_test.dart

@@ -91,4 +91,18 @@ void main() {
 
     expect(find.text('Last Selected: Blue Background'), findsOneWidget);
   });
+
+  testWidgets('MenuBar is wrapped in a SafeArea', (WidgetTester tester) async {
+    const double safeAreaPadding = 100.0;
+    await tester.pumpWidget(
+      const MediaQuery(
+        data: MediaQueryData(
+          padding: EdgeInsets.symmetric(vertical: safeAreaPadding),
+        ),
+        child: example.MenuBarApp(),
+      ),
+    );
+
+    expect(tester.getTopLeft(find.byType(MenuBar)), const Offset(0.0, safeAreaPadding));
+  });
 }

examples/api/test/material/menu_anchor/radio_menu_button.0_test.dart

@@ -74,4 +74,18 @@ void main() {
     expect(tester.widget<Radio<Color>>(find.descendant(of: find.byType(RadioMenuButton<Color>).at(2), matching: find.byType(Radio<Color>))).groupValue, equals(Colors.blue));
     expect(tester.widget<Container>(find.byType(Container)).color, equals(Colors.blue));
   });
+
+  testWidgets('MenuAnchor is wrapped in a SafeArea', (WidgetTester tester) async {
+    const double safeAreaPadding = 100.0;
+    await tester.pumpWidget(
+      const MediaQuery(
+        data: MediaQueryData(
+          padding: EdgeInsets.symmetric(vertical: safeAreaPadding),
+        ),
+        child: example.MenuApp(),
+      ),
+    );
+
+    expect(tester.getTopLeft(find.byType(MenuAnchor)), const Offset(0.0, safeAreaPadding));
+  });
 }