Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

{
        String zookeeper_node = fs::path(zc_zookeeper_path) / id / replica_name;
        LOG_TRACE(log, "Set zookeeper persistent lock {}", zookeeper_node);
        createZeroCopyLockNode(
            zookeeper, zookeeper_node, zkutil::CreateMode::Persistent,
            replace_existing_lock, path_to_set_hardlinked_files, hardlinks);
    }
}
std::pair<bool, NameSet> StorageReplicatedMergeTree::unlockSharedData(const IMergeTreeDataPart & part) const
{
    if (!part.data_part_storage || !part.isStoredOnDisk())
        return std::make_pair(true, NameSet{});
    if (!part.data_part_storage || !part.data_part_storage->supportZeroCopyReplication())
        return std::make_pair(true, NameSet{});
    
    if (part.data_part_storage->exists(IMergeTreeDataPart::FILE_FOR_REFERENCES_CHECK))
    {
        auto ref_count = part.data_part_storage->getRefCount(IMergeTreeDataPart::FILE_FOR_REFERENCES_CHECK);
        if (ref_count > 0) 
            return std::make_pair(false, NameSet{});
    }
    else
    {
        
        return std::make_pair(true, NameSet{});
    }
    return unlockSharedDataByID(part.getUniqueId(), getTableSharedID(), part.name, replica_name, part.data_part_storage->getDiskType(), getZooKeeper(), *getSettings(), log,
        zookeeper_path);
}
std::pair<bool, NameSet> StorageReplicatedMergeTree::unlockSharedDataByID(