Allow dataset row indexing with np.int types (#7423)
+1 @lhoestq can you take a look at this? The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7438). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update. Thank you
@lhoestq 
Proposed fix for #7423. Added a couple simple tests as requested. I had some test failures related to Java and pyspark even when installing with dev but these don't seem to be related to the changes here and fail for me even on clean main.

The typeerror raised when using the wrong type is: "Wrong key type: '{key}' of type '{type(key)}'. Expected one of int, slice, range, str or Iterable." I think that is fine. But I could modify the int part to something more generic (although I'm not sure what) if wanted.