[CX] ingestion status 'seqnoAdvances' field only reports one vbucket per analytics partition

The 'seqnoAdvances' field in the ingestion status api is intended to report the seqno delta that has occurred since last connect. While working on MB-46394, I observed that this field only contains one vbucket per partition- while intended to be an aggregate of all partitions, only one partition per connector is aggregated