List paid results still available to fetch back

What the caller has outstanding: in_flight for calls still running, results for finished calls whose response is still stored, newest first. Free. This is the way back in after a client-side timeout: no response arrived, so no request id was ever learned. A call is in flight for as long as the upstream takes, which is exactly when a caller who gave up is deciding whether to call again, so check here before repeating anything. Results are kept for an hour, and only for calls that were charged.