Describe the bug

Using InlineUIContainer controller inside SelectableTextBlock breaks the selection (InlineUIContainer counts as 1 character)

To Reproduce

The example from the Docs suffice if we swap TextBlock with SelectableTextBlock:

<SelectableTextBlock ClipToBounds="False" FontSize="32" TextWrapping="Wrap">
    🚀 This <Span BaselineAlignment="TextTop">example</Span> shows the <Bold>power</Bold> of
    <InlineUIContainer BaselineAlignment="Baseline">
        <Image Width="32" Height="32" VerticalAlignment="Top" Source="/Assets/avalonia-logo.ico" />
    </InlineUIContainer>
    in creating rich text displays with
    <InlineUIContainer>
        <Button Padding="0,8,0,0">
            <TextBlock ClipToBounds="False" FontSize="24" Text="👍👍🏼👍🏽👍🏾👍🏿" />
        </Button>
    </InlineUIContainer>
    inline controls 📈
</SelectableTextBlock>

An interesting case where double clicking "inline" also selects the button, the copied text reads "inline".

Expected behavior

Expected behaviour would be the selection to correctly skip InlineUIContainer elements instead of treating them like one character

Avalonia version

11.0.10

OS

Windows

Additional context

The text returned by base.Inlines?.Text inside OnPointerPressed looks correct so it might be base.TextLayout.HitTestPoint that returns an incorrect offset.