Add endpoint to get splits + configs at once
See https://github.com/huggingface/moon-landing/pull/1040#discussion_r709494993

Also evaluate doing the same for the rows (the payload might be too heavy)
Add endpoint to get splits + configs at once: See https://github.com/huggingface/moon-landing/pull/1040#discussion_r709494993

Also evaluate doing the same for the rows (the payload might be too heavy)