CheckedPopupMenuItem: Fix cursor bug and add cursor parameter

[TahaTesser]

fixes #103472

minimal code sample

import 'package:flutter/material.dart';

enum Fruits { mango, apple, banana, straberry, all }

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key, this.dark = false, this.useMaterial3 = false});

  final bool dark;
  final bool useMaterial3;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Material App',
      themeMode: dark ? ThemeMode.dark : ThemeMode.light,
      theme: ThemeData(
        useMaterial3: useMaterial3,
        brightness: dark ? Brightness.dark : Brightness.light,
        colorSchemeSeed: const Color(0xff6750a4),
      ),
      darkTheme: ThemeData(
        useMaterial3: useMaterial3,
        brightness: dark ? Brightness.dark : Brightness.light,
        colorSchemeSeed: const Color(0xff6750a4),
      ),
      home: const PopupMenuButtonSample(),
    );
  }
}

class PopupMenuButtonSample extends StatelessWidget {
  const PopupMenuButtonSample({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text(' PopupMenuButton Sample'),
      ),
      body: Center(
        child: PopupMenuButton<Fruits>(
          onSelected: (Fruits result) {},
          onCanceled: () {},
          itemBuilder: (BuildContext context) => <PopupMenuEntry<Fruits>>[
            const PopupMenuItem<Fruits>(
              value: Fruits.mango,
              child: Text('Mango'),
            ),
            const PopupMenuItem<Fruits>(
              value: Fruits.apple,
              child: Text('Apple'),
            ),
            const PopupMenuItem<Fruits>(
              value: Fruits.banana,
              child: Text('Banana'),
            ),
            const PopupMenuItem<Fruits>(
              value: Fruits.straberry,
              enabled: false,
              child: Text('Strawberry'),
            ),
            const PopupMenuDivider(),
            const CheckedPopupMenuItem<Fruits>(
              value: Fruits.all,
              child: Text('All of the above'),
            ),
          ],
        ),
      ),
    );
  }
}

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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