Don't steal focus when hovering menu bar.

Don't focus the menu item when simply hovering over a top-level menu item. The item should only be focused when the containing menu is open.

Fixes #7906

src/Avalonia.Controls/MenuItem.cs

@@ -644,7 +644,9 @@ namespace Avalonia.Controls
         /// <param name="e">The property change event.</param>
         private void IsSelectedChanged(AvaloniaPropertyChangedEventArgs e)
         {
-            if ((bool)e.NewValue!)
+            var parentMenu = Parent as Menu;
+
+            if ((bool)e.NewValue! && (parentMenu is null || parentMenu.IsOpen))
             {
                 Focus();
             }