ENH: parse complex special cases from stubs of unary functions

[ev-br]

"stub" docstrings include "special cases":

if x_i is +infinity, sqrt(x_i) is +infinity etc

test_special_cases parses these statements from docstrings and makes them into tests cases.

So far, parsing only worked for real value cases, and failed for complex-valued cases:

For complex floating-point operands, let a = real(x_i), b = imag(x_i), and
If a is either +0 or -0 and b is +0, the result is +0 + 0j.

These stanzas simply generate "case for {func} is not machine-readable" UserWarnings. Quite a wall of them.

Therefore, we update parsing and testing code to take these complex-valued cases into accout.
For now, we only consider unary functions.

The effect is that

$ ARRAY_API_TESTS_MODULE=array_api_compat.torch pytest array_api_tests/test_special_cases.py::test_unary

generates

• "128 passed, 177 warnings in 0.78s" on master
• "11 failed, 241 passed, 49 warnings in 1.82s" on this branch

So that there are new failures (from new complex-valued cases) but we have 128 less warnings.

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NB: this pull request is generated by Copilot. The original prompt and subsequent back-and-forths are at ev-br#3

[rgommers]

NB: this pull request is generated by Copilot. The original prompt and subsequent back-and-forths are at ev-br#3

Thanks @ev-br. Since it's the first such PR, I had a look - in my opinion this declaration and the level of visibility on how this code was generated is nice, and acceptable for this project. Given that this project is "advanced plumbing", I don't have any concerns about copyright, or extra review load from AI-generated contributions (you did the steering and review already).