This is mostly moving tests from activity.js
into user_search.js, but it's not a verbatim
code move.
The new module continues to make sure that
the boundary between activity and user_search
is correct, as most of the testing uses
the configuration of UserSearch from
static/js/activity.js.
It does not use a real buddy_list, though,
which simplifies some tests.
I cleaned up some tests by making sure we
were testing both sides of conditions more
rigorously.
After this change we no longer need the
bloated activity.js tests to maintain full
coverage on static/js/user_search.js.