getNamespaceMetrics includes cluster in query params

[ferhoyos]

Reviewing #6731, I have noticed that API getNamespaceMetrics sends cluster as query param, which breaks the clusterName query param convention to avoid #6322.

promiseIn = API.getNamespaceMetrics(namespace, {
        byLabels: ['request_protocol'], // ignored by prom if it doesn't exist
        cluster: cluster,
        direction: 'inbound',
        duration: props.duration,
        filters: filters,
        queryTime: props.queryTime,
        rateInterval: props.rateInterval,
        reporter: 'destination',
        step: props.step
      } as IstioMetricsOptions);

Effectively, if you hit the namespace label in the graph, cluster query param is sent: