Issue #3098399: Path alias fallback alter hook compatibility

This prepares for the alter hook approach for the path_alias module
taken in https://www.drupal.org/project/drupal/issues/3091336

language_hierarchy.module

@@ -18,6 +18,23 @@ use Drupal\language\ConfigurableLanguageInterface;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\views\ViewExecutable;
 
+/**
+ * Implements hook_module_implements_alter().
+ */
+function language_hierarchy_module_implements_alter(&$implementations, $hook) {
+  switch ($hook) {
+    case 'language_fallback_candidates_path_alias_alter':
+      // Ensure language_hierarchy_language_fallback_candidates_alter() would
+      // run after path_alias_language_fallback_candidates_path_alias_alter().
+      if (isset($implementations['language_hierarchy']) && isset($implementations['path_alias'])) {
+        $group = $implementations['language_hierarchy'];
+        unset($implementations['language_hierarchy']);
+        $implementations['language_hierarchy'] = $group;
+      }
+      break;
+  }
+}
+
 /**
  * Implements hook_language_fallback_candidates_alter().
  */