make_categories_list is extremely slow when performing course management

Using the /course/management.php page to do any course actions will lead to the 'coursecat' cache getting repeatedly purged and rebuilt over and over.

This is extremely similar to MDL-67428 but a different instance where generating all the category info at the system context would be extremely beneficial from a performance perspective, as the active filters would only need to load for 1 context, not n coursecats. This can take an extremely long time when filters are being applied to all data, as the filter chain needs to be looked up from the database for each coursecat context, and it gets immediately purged and needs to be rebuilt after an action.

This is therefore reliant on MDL-67428, and leverages the same filter setting.