Tracking remaining `2022.12` test suite coverage

[honno]

The test suite has excellent coverage of the first 2021.12 spec release, but hasn't been updated to cover all the 2022.12 additions and changes. The following is a list of things that ideally the test suite would do:

• [x] https://github.com/data-apis/array-api-tests/issues/187
  • Ideally we'd have a stubs package to use instead, i.e. https://github.com/data-apis/array-api/pull/472
  • [ ] Then we can support testing new special cases
• [x] Test the fft extension
  • We definitely want to at least test the dtype and broadcasting behaviour of these functions—and by virtue, smoke test them with valid inputs. Values testing is non-trivial enough to probably not be worth doing.

[honno]

Ofc @asmeurer and folks feel free to edit the original post, this is just what immediately came to mind.

[asmeurer]

The submodule thing also prevents the signature tests for working with any signature updates post 2022.12

We'll need to check with how the scipy stuff is going, but it's likely we'll want to prioritize fft testing, so that we can implement it numpy.array_api (https://github.com/numpy/numpy/issues/23892) and the compat library.