Revise guidance to require a minimum upper bound for supported ranks

[kgryte]

This PR

• resolves https://github.com/data-apis/array-api/issues/479 by revising the guidance requiring conforming implementations to support arrays of arbitrary rank and specifying that array libraries must support, at minimum, arrays of rank 4. Additionally, array libraries will be required to explicitly document their maximum supported rank.

Related

• https://github.com/data-apis/array-api/issues/694

[kgryte]

cc @leofang @Zac-HD

[Zac-HD]

If array libraries have a consistent way to retrieve the maximum dimensionality they support, Hypothesis can provide more informative error messages. iirc Numpy has a MAX_DIMS constant somewhere...

[kgryte]

@Zac-HD Indeed, that is part of the rationale behind https://github.com/data-apis/array-api/issues/694. Once we merge the inspection API in, we'll add support for querying the maximum number of allowed dimensions.

[rgommers]

This is pretty straightforward. I'll aim to merge this in a few days unless an objection appears.

[kgryte]

As this PR has received multiple approvals and no objections, will go ahead and merge. Any further changes can be addressed in follow-up PRs...