SetPagesVisibility and EnsureScrollBars issue

[BobLd]

Following commit makes PdfPageItemsControl unstable: SetPagesVisibility and EnsureScrollBars do not behave properly in AOT dotnet8 (behaviour is not consistent over different builds...)

26dd7d5

The attempt to fix the problem in
6bb558f

    private void OnLayoutUpdated(object? sender, EventArgs e)
    {
        LayoutUpdated -= OnLayoutUpdated;

        Dispatcher.UIThread.Post(() =>
        {
            EnsureScrollBars();

            // Ensure the pages visibility is set when OnApplyTemplate()
            // is not called, i.e. when a new document is opened but the
            // page has exactly the same dimension of the visible page
            SetPagesVisibility();
        }, DispatcherPriority.Loaded);
    }

is still unstable.

Switching to dotnet9 looks to fix the problem (difficult to assess as problem is not consistent)

[BobLd]

Hack for scroll bars is linked to issue in avalonia, should be fixed when the following is merged

AvaloniaUI/Avalonia#17461