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. 

LOG_INFO(log, "Query Profiler and TraceCollector are disabled because they cannot work without bundled unwind (stack unwinding) library.");
#endif
#if WITH_COVERAGE
    LOG_INFO(log, "Query Profiler and TraceCollector are disabled because they work extremely slow with test coverage.");
#endif
#if defined(SANITIZER)
    LOG_INFO(log, "Query Profiler disabled because they cannot work under sanitizers"
        " when two different stack unwinding methods will interfere with each other.");
#endif
#if !defined(__x86_64__)
    LOG_INFO(log, "Query Profiler and TraceCollector is only tested on x86_64. It also known to not work under qemu-user.");
#endif
    if (!hasPHDRCache())
        LOG_INFO(log, "Query Profiler and TraceCollector are disabled because they require PHDR cache to be created"
            " (otherwise the function 'dl_iterate_phdr' is not lock free and not async-signal safe).");
    std::unique_ptr<DNSCacheUpdater> dns_cache_updater;
    if (config().has("disable_internal_dns_cache") && config().getInt("disable_internal_dns_cache"))
    {
        
        DNSResolver::instance().setDisableCacheFlag();
        LOG_DEBUG(log, "DNS caching disabled");
    }
    else
    {
        
        dns_cache_updater = std::make_unique<DNSCacheUpdater>(
            global_context, config().getInt("dns_cache_update_period", 15), config().getUInt("dns_max_consecutive_failures", 5));
    }
#if defined(OS_LINUX)
    auto tasks_stats_provider = TasksStatsCounters::findBestAvailableProvider();