ingest/ledgerbackend: Create functional producer for BufferedStorageBackend #4302

Job	Run time
Test (and push) verify-range image	2m 29s
Integration tests (ubuntu-20.04, 1.21, 12, 21)	52m 13s
Integration tests (ubuntu-20.04, 1.21, 16, 21)	51m 44s
Integration tests (ubuntu-20.04, 1.22, 12, 21)	51m 37s
Integration tests (ubuntu-20.04, 1.22, 16, 21)	51m 38s
Integration tests (ubuntu-22.04, 1.21, 12, 21)	51m 3s
Integration tests (ubuntu-22.04, 1.21, 16, 21)	52m 45s
Integration tests (ubuntu-22.04, 1.22, 12, 21)	50m 49s
Integration tests (ubuntu-22.04, 1.22, 16, 21)	51m 12s
	6h 55m 30s

Provide feedback