- some copier work needs to be improved

1. clickhouse create destionation table just once if success
2. support settings_push.replication_alter_partitions_sync =1 at attach partition 
3. ...
: task_zookeeper_path(task_zookeeper_path_)
            , default_local_database(default_local_database_)
    {}
    void loadTasks(const Poco::Util::AbstractConfiguration & config, const String & base_key = "");
    
    void reloadSettings(const Poco::Util::AbstractConfiguration & config, const String & base_key = "");
    
    
    
    
    String task_zookeeper_path;
    
    String default_local_database;
    
    UInt64 max_workers = 0;
    
    Settings settings_common;
    
    Settings settings_pull;
    
    Settings settings_push;
    String clusters_prefix;
    
    TasksTable table_tasks;
    std::random_device random_device;
    pcg64 random_engine;
};
inline void DB::TaskCluster::loadTasks(const Poco::Util::AbstractConfiguration & config, const String & base_key)