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. 

{
    auto table_id = getStorageID();
    getContext()->checkTableCanBeDropped(table_id.database_name, table_id.table_name, getTotalActiveSizeInBytes());
}
void StorageReplicatedMergeTree::checkTableCanBeRenamed(const StorageID & new_name) const
{
    if (renaming_restrictions == RenamingRestrictions::ALLOW_ANY)
        return;
    if (renaming_restrictions == RenamingRestrictions::DO_NOT_ALLOW)
        throw Exception("Cannot rename Replicated table, because zookeeper_path contains implicit 'database' or 'table' macro. "
                        "We cannot rename path in ZooKeeper, so path may become inconsistent with table name. If you really want to rename table, "
                        "you should edit metadata file first and restart server or reattach the table.", ErrorCodes::NOT_IMPLEMENTED);
    assert(renaming_restrictions == RenamingRestrictions::ALLOW_PRESERVING_UUID);
    if (!new_name.hasUUID() && getStorageID().hasUUID())
        throw Exception("Cannot move Replicated table to Ordinary database, because zookeeper_path contains implicit 'uuid' macro. "
                        "If you really want to rename table, "
                        "you should edit metadata file first and restart server or reattach the table.", ErrorCodes::NOT_IMPLEMENTED);
}
void StorageReplicatedMergeTree::rename(const String & new_path_to_table_data, const StorageID & new_table_id)