MDL-78025 questions: questions_in_use should check question_references

This avoids the needs for plugins to do separate queries, which is
easier for them, and better performing.

lib/questionlib.php

@@ -29,6 +29,7 @@
  */
 
 use core_question\local\bank\question_version_status;
+use core_question\question_reference_manager;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -123,6 +124,10 @@ function questions_in_use($questionids): bool {
         return true;
     }
 
+    if (question_reference_manager::questions_with_references($questionids)) {
+        return true;
+    }
+
     // Check if any plugins are using these questions.
     $callbacksbytype = get_plugins_with_function('questions_in_use');
     foreach ($callbacksbytype as $callbacks) {