private void buildVectorRsp(ParseResult parseResult, ExprQueryRsp response) {
        MetricRspData exprRspData = new MetricRspData();
        response.setData(exprRspData);
        exprRspData.setResultType(ResultType.VECTOR);
        MetricsRangeResult matrixResult = (MetricsRangeResult) parseResult;
        response.setStatus(ResultStatus.SUCCESS);
        matrixResult.getMetricDataList().forEach(rangData -> {
            List<TimeValuePair> values = rangData.getValues();
            if (values.size() > 0) {
                MetricInstantData instantData = new MetricInstantData();
                instantData.setValue(values.get(values.size() - 1));
                instantData.setMetric(rangData.getMetric());
                exprRspData.getResult().add(instantData);
            }
        });
    }
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