MDL-67211 Tasks: Add cron_enabled setting.

Co-authored-by: Sam Marshall <s.marshall@open.ac.uk>

lib/outputlib.php

@@ -270,6 +270,16 @@ function theme_reset_all_caches() {
     }
 }
 
+/**
+ * Reset static caches.
+ *
+ * This method indicates that all running cron processes should exit at the
+ * next opportunity.
+ */
+function theme_reset_static_caches() {
+    \core\task\manager::clear_static_caches();
+}
+
 /**
  * Enable or disable theme designer mode.
  *