FocusItemByFullPath replaces selection

Hi Mike,

We have a way where you can prevent selection change notifications until a "batch" is complete.  This would allow you to effectively restore the prior selection before any selection change events go.

I tested with this kind of code where I selected three items and then executed this code that focused the second one.  All three items were selected at the end of the batch.

using (var batch = treeListBox.CreateSelectionBatch()) {
	var oldSelectedItems = treeListBox.SelectedItems.ToArray();
					
	treeListBox.FocusItem(treeListBox.SelectedItems[1]);
					
	foreach (TreeNodeModel item in oldSelectedItems)
		item.IsSelected = true;
}

Thanks - that seems to work around the problem, and could be a useful pattern for us elsewhere.