If a name change event arrived during the call to
fetch_initial_state_data(), we would call apply_events() to
update the data structure that eventually becomes page_params.
Our update code, instead of surgically updating the fields, was
just overwriting the record, which led to is_bot being taken
out of the record when only full_name was in the event.
Apart from fixing the "update" case to do the right thing,
this commit also does a bit of cleanup on the code handling
"realm_user" events to make it more generic in how it does
add/remove/update. If we could standardize our events a bit
more, this could eventually lead to DRYing up some of the
apply_events() code.
(imported from commit 772e2fcd6a5605ccb6e8d1bc499b5f336934cf3c)