PG19: fix follower cluster status replies

[ibrahim halatci (ihalatci)]

Summary

• send WAL receiver apply-status replies once per second in the Perl follower-cluster test harness
• match the existing Python test harness behavior
• preserve PostgreSQL and Citus production defaults

Provenance

• published from the explicitly approved commit 5e4ddc836a95df6cea9cceef33cb44d48559b736
• based directly on pg19-support at ff8f1f8c46de4c3ed094c99796c9805529d1a328
• contains only the one-line wal_receiver_status_interval=0 to 1 test-harness change

Testing

• PG19beta2 before fix: make -C src/test/regress check-follower-cluster timed out after 180 seconds while creating the follower topology
• PG17.10 after fix: 8/8 follower-cluster tests passed
• PG18.4 after fix: 8/8 follower-cluster tests passed
• PG19beta2 after fix: 8/8 follower-cluster tests passed

Closes #8736

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.79%. Comparing base (ff8f1f8) to head (5e4ddc8).

Additional details and impacted files

@@               Coverage Diff                @@
##           pg19-support    #8738      +/-   ##
================================================
- Coverage         88.80%   88.79%   -0.02%     
================================================
  Files               288      288              
  Lines             64416    64416              
  Branches           8100     8102       +2     
================================================
- Hits              57206    57199       -7     
- Misses             4873     4877       +4     
- Partials           2337     2340       +3     

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