arrivals_departures/connections: make fast again ⚡️

by adding indexes on stop_times.{arrival,departure}_time with `NULLS LAST`, as introduced by b2001e3.

follow-up of b2001e3

Author: derhuerst

lib/stop_times.js

@@ -108,6 +108,9 @@ AND "${opt.schema}".stop_times.stop_sequence = t.stop_sequence;
 
 CREATE INDEX ON "${opt.schema}".stop_times (stop_sequence_consec);
 CREATE INDEX ON "${opt.schema}".stop_times (trip_id, stop_sequence_consec);
+CREATE INDEX ON "${opt.schema}".stop_times (arrival_time DESC NULLS LAST);
+CREATE INDEX ON "${opt.schema}".stop_times (departure_time DESC NULLS LAST);
+-- todo: are these two necessary?
 CREATE INDEX ON "${opt.schema}".stop_times (arrival_time);
 CREATE INDEX ON "${opt.schema}".stop_times (departure_time);