ENH: add setdiff1d

[lucascolley]

These functions look like the most obvious candidates for this library from scikit-learn: https://github.com/scikit-learn/scikit-learn/blob/439ea045ad44e6a09115dc23e9bf23db00ff41de/sklearn/utils/_array_api.py#L931-L982

cc @OmarManzoor @ogrisel @betatim

[lucascolley]

One problem is that these functions make use of device from array-api-compat. Either we need to restrict support in this library to array objects with the device attribute, or we vendor (copy) device and the functions it calls from array-api-compat.

[asmeurer]

I would propose isin for inclusion in the standard.

[lucascolley]

any thoughts on setdiff1d @asmeurer ?

[asmeurer]

I've never even heard of that function before. I guess if it has a lot of usage it could be proposed too, but otherwise I would assume it's a more niche function that would be more appropriate for this package. Also, isn't it straightforward to implement in terms of isin if that were added (though perhaps inefficiently)?

[lucascolley]

In scikit-learn they implement both in terms of in1d

[rgommers]

I'd also say that setdiff1d is too niche to consider for the standard. Adding it to array-api-extra seems like a better option.