MDL-46147 modinfo: performance improvement for course page

This is a big win in a specific situation, ie filters enabled for content+headings,
and no activity descriptions visible on the course page.

lib/modinfolib.php

@@ -1323,6 +1323,10 @@ class cm_info implements IteratorAggregate {
         if (!isset($options['context'])) {
             $options['context'] = $this->get_context();
         }
+        // Improve filter performance by preloading filter setttings for all
+        // activities on the course (this does nothing if called multiple
+        // times).
+        filter_preload_activities($this->get_modinfo());
         return format_string($this->get_name(), true,  $options);
     }