The original include_subscribers implementation did not correctly
update the apply_events code path to avoid adding 'subscribers' dicts
to things. This corrects that oversight.
There's a new option, `include_subscribers`, that controls whether the
API sends down subscriber data for the various streams you are
subscribed to.
This has significant performance savings for large realms with naive
clients, and saves a bunch of bandwidth as well.
This moves do_events_register, fetch_initial_state_data and friends to
a new file.
Modified significantly by tabbott for correctness and to remove unused
imports.
Fixes#3635.
Steve Howell
Tim Abbott
Harshit Bansal
paxapy
saisrivathsa