Add EnumOptionAttribute

[Poker-sang]

Use:

[ToolkitSampleEnumOption<Visibility>("MyVisibility", Title = "Visibility")]
public partial class Sample : UserControl;

instead of

[ToolkitSampleEnumOption("MyVisibility", "Visible", "Collapsed", Title = "Visibility")]
public partial class Sample : UserControl;

And generate accurate enum type for ToolkitSampleEnumOption:

public Windows.UI.Xaml.Controls.Visibility MyVisibility
{
    get => (Windows.UI.Xaml.Controls.Visibility)(...)!.Value!;
    set ...
}

All the changes are AOT compatiable