This fixes the most core data structures inside of
muting.js. We still use stream names for incoming
data to set_muted_topics and outgoing data from
get_muted_topics.
This will make us more resilient to stream name changes.
Before, if you were logged on when a stream rename
occured, topics that were muted under that stream would
appear to be unmuted. (You could fix it with a reload,
but it can be jarring to have a bunch of unread messages
appear in your feed suddenly.)
Fixes#11033
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.)