Reconnection is now handed by cancelling the connCtx context. This is a lot cleaner and the jetstream client package honors context cancellation. Saving of last time_us is also simplified now. We only save (update, rather) after the last seen event by incrementing the event's time_us by 1 (this is ok since it's a monotonic clock). We pick up from here upon reconnect and don't save last time_us for any other reason. Lastly, outside of first boot, we should only ever use UpdateLastTimeUs.