Add a command that will freeze clickhouse-server process with STOP signal and wakeup it after specified amount of time.
This is needed for testing (fault injection).

Wakeup can be done with `ShellCommand` running `sleep N && kill -CONT pid`
}
        case Type::RELOAD_DICTIONARY: [[fallthrough]];
        case Type::RELOAD_DICTIONARIES: [[fallthrough]];
        case Type::RELOAD_EMBEDDED_DICTIONARIES:
        {
            required_access.emplace_back(AccessType::SYSTEM_RELOAD_DICTIONARY);
            break;
        }
        case Type::RELOAD_CONFIG:
        {
            required_access.emplace_back(AccessType::SYSTEM_RELOAD_CONFIG);
            break;
        }
        case Type::RELOAD_SYMBOLS:
        {
            required_access.emplace_back(AccessType::SYSTEM_RELOAD_SYMBOLS);
            break;
        }
        case Type::STOP_MERGES: [[fallthrough]];
        case Type::START_MERGES:
        {
            if (query.table.empty())
                required_access.emplace_back(AccessType::SYSTEM_MERGES);
            else
                required_access.emplace_back(AccessType::SYSTEM_MERGES, query.database, query.table);
            break;
        }
        case Type::STOP_TTL_MERGES: [[fallthrough]];
        case Type::START_TTL_MERGES:
        {