private NodeManager getNodeManager() {
    return configManager.getNodeManager();
  }
Generate a RegionGroups' allocation plan({@link CreateRegionGroupsPlan})

@param allotmentMap Map<DatabaseName, RegionGroup allotment>
@param consensusGroupType {@link TConsensusGroupType} of the new RegionGroups
@return CreateRegionGroupsPlan
@throws NotEnoughDataNodeException When the number of DataNodes is not enough for allocation
@throws DatabaseNotExistsException When some StorageGroups don't exist
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/manager/load/balancer/RegionBalancer.java