@TestOnly
    public void setStartTime(Long startTime) {
      this.startTime = startTime;
    }
If there is a ReleaseTask or FlushTask, block the current thread to wait up to
MAX_WAITING_TIME_WHEN_RELEASING. The thread will be woken up if the ReleaseTask or FlushTask
ends or the wait time exceeds MAX_WAITING_TIME_WHEN_RELEASING.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/memory/ReleaseFlushMonitor.java