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. 

{
    ReadLock lock{rwlock, getLockTimeout(local_context)};
    if (!lock)
        throw Exception("Lock timeout exceeded", ErrorCodes::TIMEOUT_EXCEEDED);
    return file_checker.check();
}
void StorageStripeLog::truncate(const ASTPtr &, const StorageMetadataPtr &, ContextPtr, TableExclusiveLockHolder &)
{
    disk->clearDirectory(table_path);
    indices.clear();
    file_checker.setEmpty(data_file_path);
    file_checker.setEmpty(index_file_path);
    indices_loaded = true;
    num_indices_saved = 0;
    getContext()->dropMMappedFileCache();
}
void StorageStripeLog::loadIndices(std::chrono::seconds lock_timeout)
{
    if (indices_loaded)
        return;
    
    
    WriteLock lock{rwlock, lock_timeout};
    if (!lock)
        throw Exception("Lock timeout exceeded", ErrorCodes::TIMEOUT_EXCEEDED);
    loadIndices(lock);
}
void StorageStripeLog::loadIndices(const WriteLock & lock )