[ROS][refact] Change hesai frame_id to hesai_lidar
The config file of hesai driver set default frame_id as hesai_lidar
Please see the link here: https://github.com/HesaiTechnology/HesaiLidar_ROS_2.0/blob/941b3c550fe81c6cfdbef88a12f87b30820c00d5/config/config.yaml#L21
So we keep this value in the slam launch file of hesai.