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`
START_REPLICATED_SENDS,
        STOP_REPLICATION_QUEUES,
        START_REPLICATION_QUEUES,
        FLUSH_LOGS,
        FLUSH_DISTRIBUTED,
        STOP_DISTRIBUTED_SENDS,
        START_DISTRIBUTED_SENDS,
        END
    };
    static const char * typeToString(Type type);
    Type type = Type::UNKNOWN;
    String target_dictionary;
    String database;
    String table;
    String replica;
    String replica_zk_path;
    bool is_drop_whole_replica;
    String storage_policy;
    String volume;
    String getID(char) const override { return "SYSTEM query"; }
    ASTPtr clone() const override { return std::make_shared<ASTSystemQuery>(*this); }
    ASTPtr getRewrittenASTWithoutOnCluster(const std::string & new_database) const override
    {
        return removeOnCluster<ASTSystemQuery>(clone(), new_database);
    }
protected:
    void formatImpl(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override;
};
}