Unnecessary loading of avatars due to after_initialize hook
While investigating #325226 (closed), I noticed that we were loading lots of avatars unnecessarily.
This is due to the #add_avatar_to_batch
that we do every time an Avatarable
is initialized.
https://gitlab.com/gitlab-org/gitlab/blob/8ffb34df6fef1b73f6f779363cad4aee8c674e72/app/models/concerns/avatarable.rb#L22
This means, even if we don't need the avatar for some or most of these objects, we're still loading all of them from the DB.