ButtonSpinnerLocation does not work with Simple theme

[stogle]

Describe the bug

Setting ButtonSpinner's ButtonSpinnerLocation to Location.Left has no effect when using the Simple theme.

To Reproduce

Steps to reproduce the behavior:

      <ButtonSpinner Height="30" ButtonSpinnerLocation="Left">
        <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" Text="Everest"/>
      </ButtonSpinner>

Expected behavior

Setting ButtonSpinner's ButtonSpinnerLocation to Location.Left should move the spinner buttons to the left side of the content.

Environment

• Windows 11
• Avalonia-Version: 11.0.x

Additional context

The selector in ButtonSpinner.xaml is incorrect. Instead of

Avalonia/src/Avalonia.Themes.Simple/Controls/ButtonSpinner.xaml

Line 74 in 8c23a35

<Style Selector="^ /template/ StackPanel#PART_SpinnerPanel">

it should be

      <Style Selector="^ /template/ UniformGrid#PART_SpinnerPanel">

[timunie]

@stogle can you file a PR to solve this? Would be appreciated.

[stogle]

@timunie I created #13142 for this.