We now use stream_id as our key to rename streams, which
should prevent a few race conditions long term. (We are
still possibly contending with other events that use
stream_name as a key, so this is not perfect.)
This function will make it easier to unit test upcoming
changes related to stream counts.
This was mostly moving code, but one change is that we
don't call create_subs() in subs.js any more (which would
have been kind of circular dependency), since the only thing
that it did besides calling a more appropriate function
in stream_data.js was to generate a trigger that was
subsequently ignored and possibly a UI trap, as we don't
want to be messing with the stream sidebar when we go into
the stream settings page.
We now simply call exports.create_sub_from_server_data() for
newly encountered unsubscribed streams (which don't belong in
the sidebar anyway.)
This function used to live in subs.js. It's mostly a code move,
but I simplified the logic to determine whether it's subscribed
not to do a lookup into the same data structure that the sub
already came from.
I also added some tests.