MDL-57273 persistent: Some more magic __call conversions

I missed all the entry pages when converting from set_abc() and get_abc() to set('abc', ) and get('abc').

Also fixed a wrong namespace for core_competency\external\performance_helper

lib/classes/form/persistent.php

@@ -254,7 +254,7 @@ abstract class persistent extends moodleform {
             $data = static::convert_fields($data);
 
             // Ensure that the ID is set.
-            $data->id = $this->persistent->get_id();
+            $data->id = $this->persistent->get('id');
         }
         return $data;
     }