public Timer timer(
      long delta, TimeUnit timeUnit, String name, MetricLevel metricLevel, String... tags) {
    Timer timer = getOrCreateTimer(name, metricLevel, tags);
    timer.update(delta, timeUnit);
    return timer;
  }
Update timer. if exists, then update timer by delta and timeUnit. if not, then create and
update

@param delta the value to update
@param timeUnit the unit of delta
@param name the name of name
@param metricLevel the level of name
@param tags string pairs, like sg="ln" will be "sg", "ln"
iotdb-core/metrics/interface/src/main/java/org/apache/iotdb/metrics/AbstractMetricManager.java