[Profile Emails] Allow college members to set primary addresses ONLY for non-registered profiles
Currently, all Editorial College members have the scipost.can_validate_profile_emails
permission, which allows them to mark profile addresses as primary. This power should be limited to the subset of profiles without an active contributor account associated to them, for which no greater authority exists. In the case of registered users, they alone should be the actors capable of setting their primary communication address, now easily accessible via the email preferences pane.