Update for M3.9 to implement the component_gradeitems class

[logan-reynolds]

When using this plugin on Moodle 3.9 the following debug messages are output:

Components supporting advanced grading should be updated to implement the component_gradeitems class
line 312 of /grade/grading/lib.php: call to debugging()
line 345 of /grade/grading/lib.php: call to grading_manager::available_areas()
line 359 of /course/modlib.php: call to grading_manager->get_available_areas()
line 180 of /course/modlib.php: call to edit_module_post_actions()
line 154 of /course/modedit.php: call to add_moduleinfo()

[thepurpleblob]

Also applies to Moodle 3.8

[thepurpleblob]

...and 3.10 and 3.11