Make special case tests only use relevant arrays

[honno]

Right now we generate arrays irrelevant to test cases, e.g. arrays with no NaNs in a test case about NaN behaviour. A low-priority thing is to generate test cases which are relevant to the test case (either by xps.arrays(..., elements={...}) or xps.arrays(...).filter(...)). Probably requires some significant reworking of generate_stubs.py.

To quote myself from #38:

It seems like the only problem with numpy.array_api (when running 2000 examples) is in-place addition.

>>> x1 = xp.asarray(-0.0)
>>> x1
Array(-0., dtype=float64)
>>> x2 = xp.asarray(-0.0)
>>> xp.add(x1, x2)
Array(-0., dtype=float64)
>>> x1 + x2
Array(-0., dtype=float64)
>>> x1 += x2
>>> x1
Array(0., dtype=float64)  # not negative 0, like it is with xp.add() and __add__()

Interestingly I had to run like 200 examples to get this error consistently. Something for the future would be to filter strategies from the @given() level so that only arrays with NaNs/infs/whateverproperty-we're-testing are generated, which would mitigate this problem.

[honno]

Resolved by #104