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. 

#include <Backups/BackupEntriesCollector.h>
#include <Backups/IBackup.h>
#include <Backups/IBackupCoordination.h>
#include <Backups/IBackupEntry.h>
#include <Backups/IRestoreCoordination.h>
#include <Backups/RestorerFromBackup.h>
#include <Poco/DirectoryIterator.h>
#include <base/scope_guard.h>
#include <Common/scope_guard_safe.h>
#include <boost/algorithm/string/join.hpp>
#include <boost/algorithm/string/replace.hpp>
#include <boost/algorithm/string.hpp>
#include <algorithm>
#include <ctime>
#include <filesystem>
#include <iterator>
#include <numeric>
#include <thread>
#include <future>
namespace fs = std::filesystem;
namespace ProfileEvents
{
    extern const Event ReplicatedPartFailedFetches;
    extern const Event ReplicatedPartFetchesOfMerged;
    extern const Event ObsoleteReplicatedParts;
    extern const Event ReplicatedPartFetches;
    extern const Event CreatedLogEntryForMerge;
    extern const Event NotCreatedLogEntryForMerge;
    extern const Event CreatedLogEntryForMutation;
    extern const Event NotCreatedLogEntryForMutation;