成员的完整列表，这些成员属于 NIMQChatChannelSubscribeResp,包括所有继承而来的类成员

failed_channels	NIMQChatChannelSubscribeResp
failed_channels_count	NIMQChatChannelSubscribeResp
res_code	NIMQChatChannelSubscribeResp
unread_infos	NIMQChatChannelSubscribeResp
unread_infos_count	NIMQChatChannelSubscribeResp
user_data	NIMQChatChannelSubscribeResp