Split update hooks

Closes #3472203

menu_link_attributes.install

@@ -81,7 +81,7 @@ function menu_link_attributes_update_8001(&$sandbox) {
 }
 
 /**
- * Add labels and description to default menu item attributes for clarification.
+ * Add "Container class(es)" attribute to default attributes.
  */
 function menu_link_attributes_update_8002(): void {
   $attributes = \Drupal::configFactory()
@@ -96,7 +96,20 @@ function menu_link_attributes_update_8002(): void {
     ];
   }
 
-  // Only set if still existing in custom config:
+  \Drupal::configFactory()
+    ->getEditable('menu_link_attributes.config')
+    ->set('attributes', $attributes)->save();
+}
+
+/**
+ * Add labels and description to default menu item attributes for clarification.
+ */
+function menu_link_attributes_update_8003(): void {
+  $attributes = \Drupal::configFactory()
+    ->get('menu_link_attributes.config')
+    ->get('attributes');
+
+  // Only set labels and description if still existing in custom config:
   if (isset($attributes['class'])) {
     // Only set if not yet set custom:
     if (empty($attributes['class']['label'])) {