maint(coord): change card metric_ prefix to tenant_

[alextheimer]

Pull Request checklist

• [x] The commit(s) message(s) follows the contribution guidelines ?
• [ ] Tests for the changes have been added (for bug fixes / features) ?
• [ ] Docs have been added / updated (for bug fixes / features) ?

Change TenantIngestionMetering cardinality metric label names:

metric_ws -> _tenant_ws_
metric_ns -> _tenant_ns_

and also add the label

_audience_ -> "tenants"