Make sure that the scheduled task really updates all cohorts

[abias]

It has been reported outside Github that the scheduled task apparently does not update all existing cohorts / rules for all users. There may be cases when a user's profile field value is changed, his cohort memberships are not updates until his next login even though the schedule task runs properly in the meantime.

This behaviour should be investigated.

[christianabila]

The scheduled task update_cohorts only runs, if changes to the profile cohort form have been made (based off c9ffb35)

• local/profilecohort/classes/profilecohort.php:413
• local/profilecohort/classes/task/update_cohorts.php:50

I guess it's a safeguard for performance reasons?

Also, in the case of auth_db, user update events are suppressed in the core code https://github.com/moodle/moodle/blob/main/auth/db/auth.php#L395 - so automatic updates to the cohorts are not done at all.