Menu items do not have position information when created via ItemsSource

### Description

When a menu is populated with menu items in XAML, Windows Narrator can get the position info of each menu item and will announce them when focused.

However, when the menu items are generated from `ItemsSource`. The narrator won't be able to get position info and therefore won't announce it
```

```

More specifically, `MenuItemAutomationPeer` throws exceptions in `GetPositionInSet` and `GetSizeOfSet` if `ItemsSource` is used.

### Reproduction Steps

1. Create a menu with `ItemsSource` bound to a collection of string
2. Run the application.
3. Run Windows Narrator
4. Tab over the menu items

### Expected behavior

The narrator should announce the header of a menu item as well as its position, e.g. 3 of 5

### Actual behavior

Only the header is announced by the narrator

### Regression?

_No response_

### Known Workarounds

_No response_

### Impact

_No response_

### Configuration

_No response_

### Other information

_No response_