[FIX] base, mail: ensure ordering of search on partner / user

Add 'id' in partner ordering, to be sure searching on duplicated partners is
deterministic.

In mail, use standard ordering when searching on users to be deterministic.
As ordering on users is based on name then login which is unique, this is a
safe ordering and can be used as it.

Task-2612945 (Mail: Defensive email formatting)

Part-of: odoo/odoo#74474