Our logic for stream_has_topics never accounted for
us creating essentially "empty" stream buckets that
don't have topics, but we recently added some code
related to unread counts that violated the original
assumptions of the code.
Now we check deeper into the stream bucket to find
actual topics.
This bug manifested in the left sidebar where users
were seeing streams as recently active just because
some muted topics had unread counts, when in fact
the stream was inactive for practical purposes.
This run_test helper sets up a convention that allows
us to give really short tracebacks for errors, and
eventually we can have more control over running
individual tests. (The latter goal has some
complications, since we often intentionally leak
setup in tests.)
This mostly moves code, and it also removes some unnecessary
coupling to stream_data.js. The topic_data code purely
works in the stream_id space, so there's no need to set up
actual stream data for it.