presence: Report presence before /register request.
presence: Report presence before /register request.

The /register request fetching initial data can get a lot of data and
take some time.  In the meantime, the user may have started typing and
other users may see activity from them, so it looks buggy if we show
their status as offline.

Part of #3590.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile