mediawiki.user: Use mw.log.deprecate to track user() and anonymous()

Follows-up I5970be9e859358 which deprecated these originally.

Also remove obsolete tests now that they're linked by reference.

Change-Id: I559efa8a61de9f7b600c7b74edd5a56fb0a33b00
(cherry picked from commit de5e13598a79b3876de3902f5985a3bf0bd0d6a0)
Merge "mediawiki.user: Use mw.log.deprecate to track user() and anonymous()" into wmf/1.24wmf5