private MetricInfo buildMetricInfoFromTraffic(String metricName, Endpoint endpoint) {
        MetricInfo metricInfo = new MetricInfo(metricName);
        metricInfo.getLabels().add(new LabelValuePair(LabelName.ENDPOINT.getLabel(), endpoint.getName()));
        metricInfo.getLabels().add(new LabelValuePair(LabelName.SCOPE.getLabel(), Scope.Endpoint.name()));
        return metricInfo;
    }
OAP adopt time step by start/end,
reserve step/timeout param to keep consistent with API protocol.
oap-server/server-query-plugin/promql-plugin/src/main/java/org/apache/skywalking/oap/query/promql/handler/PromQLApiHandler.java