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 <Server/ProtocolServerAdapter.h>
#include <Server/HTTP/HTTPServer.h>
#include <Interpreters/AsynchronousInsertQueue.h>
#include <filesystem>
#include "config_core.h"
#include "Common/config_version.h"
#if defined(OS_LINUX)
#    include <sys/mman.h>
#    include <sys/ptrace.h>
#    include <Common/hasLinuxCapability.h>
#endif
#if USE_SSL
#    include <Poco/Net/Context.h>
#    include <Poco/Net/SecureServerSocket.h>
#endif
#if USE_GRPC
#   include <Server/GRPCServer.h>
#endif
#if USE_NURAFT
#    include <Coordination/FourLetterCommand.h>
#    include <Server/KeeperTCPHandlerFactory.h>
#endif
#if USE_JEMALLOC
#    include <jemalloc/jemalloc.h>
#endif
namespace CurrentMetrics
{
    extern const Metric Revision;
    extern const Metric VersionInteger;
    extern const Metric MemoryTracking;