services/horizon: Resume ingestion immediately when catching up (#4196)

When more than one ingesting instances is running and the current one is behind,
go to `resumeState` immediately instead of after 1s. Waiting 1s can slow down
make applying ledgers by Captive-Core slower in catching-up mode.

services/horizon/internal/ingest/fsm.go

@@ -424,9 +424,8 @@ func (r resumeState) run(s *system) (transition, error) {
 			log.WithError(err).Warn("error updating stellar-core cursor")
 		}
 
-		return retryResume(resumeState{
-			latestSuccessfullyProcessedLedger: lastIngestedLedger,
-		}), nil
+		// resume immediately so Captive-Core catchup is not slowed down
+		return resumeImmediately(lastIngestedLedger), nil
 	}
 
 	ingestVersion, err := s.historyQ.GetIngestVersion(s.ctx)

services/horizon/internal/ingest/resume_state_test.go

@@ -316,7 +316,7 @@ func (s *ResumeTestTestSuite) TestBumpIngestLedger() {
 	s.Assert().Equal(
 		transition{
 			node:          resumeState{latestSuccessfullyProcessedLedger: 101},
-			sleepDuration: defaultSleep,
+			sleepDuration: 0,
 		},
 		next,
 	)