fix(ListView): Update SelectedIndex on selection via container

src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBase.cs

@@ -102,6 +102,7 @@ private void OnSelectedItemsCollectionChanged(object sender, NotifyCollectionCha
 			{
 				_modifyingSelectionInternally = true;
 				SelectedItem = SelectedItems.Where(item => items.Contains(item)).FirstOrDefault();
+				SelectedIndex = items.IndexOf(SelectedItem);
 
 				TryUpdateSelectorItemIsSelected(validRemovals, false);
 				TryUpdateSelectorItemIsSelected(validAdditions, true);