private List<String> buildLabelValuesFromQuery(List<MetricsValues> metricsValues, String labelName) {
        Set<String> labelValues = new LinkedHashSet<>();
        metricsValues.forEach(metricsValue -> {
            DataLabel dataLabel = new DataLabel();
            dataLabel.put(metricsValue.getLabel());
            labelValues.add(dataLabel.get(labelName));
        });
        return Arrays.asList(labelValues.toArray(new String[0]));
    }
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