Reduce data fetched by message_search_users

When searching for non-contacts the messaging API message_search_users method gets data for most of the user fields to check if the user is visible.

A lot of the data fetched is not needed to check the visibility of the user and is then discarded unused.

We should reduce the amount of data required to a minimum.

Note this was originally planned for MDL-63983 but it was late to accept it there (near rolling), so was agreed to create this followup to close the circle.