Fix heavy load on the /topics endpoint when the terminal app is started up #493
Description
See zulip/zulip#13726 for some background on the performance impact of the GET /topics query.
The current behavior of the terminal app is to fetch the full topic history of every subscribed stream on startup using the GET /topics endpoint. This is fairly expensive, and not in line with how the webapp works (where we only fetch full/old topic history via "more topics"). I'm not sure what the right solution is (I hesitate a bit to recommend that the mobile app copy the webapp's behavior of fetching the most recent 1K+ messages of overall history and use the topics from those), but we should figure out a way to make terminal app startup better.