Raise error for incorrect JSON serialization
PTAL @lhoestq @albertvillanova  The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7273). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.
Raise error when `lines = False` and `batch_size < Dataset.num_rows` in `Dataset.to_json()`.

Issue: #7037 

Related PRs:
#7039 #7181 