rename or alias get_namespace to array_namespace

[ntessore]

Having a function array_namespace seems more intuitive than get_namespace, mainly due to symmetry with e.g. repr(), str(), iter(), next(), since array_namespace(x) returns x.__array_namespace__() if it exists, and does something sensible if it does not.

[rgommers]

Thanks for the suggestion @ntessore. On the one hand, I can see that the name may be slightly nicer. On the other hand, this package is already past version 1.0, and the get_namespace name is already used in other places (e.g., https://numpy.org/neps/nep-0047-array-api-standard.html). So I'm not sure that this is worth the churn.

[ntessore]

That's expected, of course, but I thought I should bring this up at least while the NEP is still a draft.

[asmeurer]

I agree it does seem like a better name to match __array_namespace__. We would probably want to keep get_namespace too if we change it just because we did already do a release with it.

[asmeurer]

I'm actually in favor of this, but I've made it as a separate PR in case there are any objections #29. I kept get_namespace as an (undocumented) backwards compatible wrapper.