A Bug with the Android Back Button in 9.x.x versions

### Description

The back button in Android doesn't trigger **DispatchKeyEvent** or even the **OnBackPressedDispatcher** if it registers a callback.

### Steps to Reproduce

1. Add latest Microsoft.Maui.Controls package (9.x.x) to a new Maui Blazor project targets .net9
2. Add a new Maui page
3. Add a logic to navigate to that page
```csharp
await App.Current.Windows[0].Navigation.PushModalAsync(new NewPage1());
```
5. Override the DispatchKeyEvent in the MainActivity to capture the back button for example
### Link to public reproduction project repository

https://github.com/abdelrahman-ali-intact/MacrosoftMauiControls9040_Test.git

### Version with bug

9.0.40 SR4

### Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

### Last version that worked well

8.0.100 SR10

### Affected platforms

Android

### Affected platform versions

_No response_

### Did you find any workaround?

No

### Relevant log output

```shell

```

Start with the linked MacrosoftMauiControls9040_Test reproduction and the MainActivity DispatchKeyEvent override, then compare Android back-button behavior in Microsoft.Maui.Controls 9.0.40 SR4 with 8.0.100 SR10. Check how the OnBackPressedDispatcher callback behaves after PushModalAsync; done means the back button reaches the expected handler in the reproduced .NET 9 MAUI Blazor scenario.

Written by the indexing model from the issue text.