[Proposal] Expander animation

### Feature name

Expander updated to support animation via a new ExpanderAnimationBehavior

```c#
public partial class ExpanderAnimationBehavior : BaseBehavior, IExpansionController
{
[BindableProperty] public partial Easing CollapsingEasing { get; set; } = Easing.Linear;
[BindableProperty] public partial uint CollapsingLength { get; set; } = 250u;
[BindableProperty] public partial Easing ExpandingEasing { get; set; } = Easing.Linear;
[BindableProperty] public partial uint ExpandingLength { get; set; } = 250u;
// ...
}
```

### Link to discussion

https://github.com/CommunityToolkit/Maui/discussions/1628

### Progress tracker

- [x] Android Implementation
- [x] iOS Implementation
- [x] MacCatalyst Implementation
- [x] Windows Implementation
- [ ] Tizen Implementation
- [x] Unit Tests
- [x] Samples
- [ ] Documentation (TODO)

### Summary

This issue and the corresponding PR is to continue a conversation that started in the discussion forums on how we may introduce animations to the Expander component.

### Motivation

The Expander component could be improved to support animation.

### Detailed Design

[Feb 15, 2025, Original Design]
[April 5, 2025, Refactor/Rewrite]

[March 2, 2026, Refactor/Rewrite]

Wrap the user's `Expander.Content` inside a new `Expander.ContentHost` (ContentView) so that we can implement expanding/collapsing animation by manipulating `Expander.ContentHost.HeightRequest`.

Usage:

```xaml

```

### Drawbacks

_No response_

### Unresolved Questions

_No response_