public synchronized MemoryManager getOrCreateMemoryManager(
      String name, long totalMemorySizeInBytes) {
    return getOrCreateMemoryManager(name, totalMemorySizeInBytes, false);
  }
Try to create a new memory manager with specified name and total memory size in bytes, then put
it into children map. NOTICE: if there are same name memory manager, it will return the
existing one.

@param name the name of memory manager
@param totalMemorySizeInBytes the total memory size in bytes of memory manager
@return the memory manager
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/memory/MemoryManager.java