We now trigger an event in user_events.js, and we dynamically
build the list of names in pm_list.js by calling out to
people.get_recipients().
We have a few variations of functions that build lists of names
for huddles, which should be cleaned up eventually. They are
called at different times in the code path, so the different
functions, while doing mostly the same thing, start with different
data sources.
Some of the work here was done Tomasz Kolek.
When we click on "more conversations" in "Private Messages,"
we call it being "zoomed in." Before this change, when
new PMs arrived, we would rebuild the list and zoom out
again. Now we track the zoomed_in state with a variable.
Also, if you are zoomed in and switch from one PM narrow
to another, we also keep you zoomed in.
This fix also removes some extraneous/redundant code.
Fixes: #2561
We now use comma-delimited lists of user_ids for the following
data structures in unread.js:
- unread_privates[<user_ids_string>]
- get_counts.pm_count[<user_ids_string>]
