private static long formatTimestamp2Millis(String timestamp) {
        long time;
        try {
            // if Unix timestamp in seconds, such as 1627756800
            time = Double.valueOf(timestamp).longValue() * 1000;
        } catch (NumberFormatException e) {
            // if RFC3399 format, such as 2024-09-19T20:11:00.781Z
            time = ISODateTimeFormat.dateTime().parseMillis(timestamp);
        }
        return time;
    }
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