Update the client (moonlanding) to use /splits-next and /first-rows
Create a PR on moonlanding to:
  - [x] use the new /splits-next and /first-rows endpoints instead of /splits and /rows -> https://github.com/huggingface/moon-landing/pull/3650
  - [x] adapt the design to handle better the error cases (400 -> Dataset Error, open a discussion, 500 -> Server Error, retry or open an issue) + the format has changed a bit -> not handled here, see https://github.com/huggingface/moon-landing/issues/3721
  - [x] discovery of the API: show the query + link to the doc (https://huggingface.co/docs/datasets-server/api_reference), so that the users can start using the API -> not handled here, see https://github.com/huggingface/moon-landing/issues/3722

Update the client (moonlanding) to use /splits-next and /first-rows: Create a PR on moonlanding to:
  - [x] use the new /splits-next and /first-rows endpoints instead of /splits and /rows -> https://github.com/huggingface/moon-landing/pull/3650
  - [x] adapt the design to handle better the error cases (400 -> Dataset Error, open a discussion, 500 -> Server Error, retry or open an issue) + the format has changed a bit -> not handled here, see https://github.com/huggingface/moon-landing/issues/3721
  - [x] discovery of the API: show the query + link to the doc (https://huggingface.co/docs/datasets-server/api_reference), so that the users can start using the API -> not handled here, see https://github.com/huggingface/moon-landing/issues/3722
