Major Description
We need a way to pull the known down partition counts out of DifferenceWithIdealState when an instance is offline, reducing the alert volume to solely the down instance notification. Without metrics from helix indicating the number of partitions hosted on a given participant, we can't reason as to which "DifferenceWithIdealState" counts are supposed to be down and which are an actually difference caused by something other than a node outage.
These should be produced on a per-participant, per-resource basis (ie., helix.i001.participantstatus.cluster.host.db.partitiongauge = 64 or whatever)