Add support for PEP 702

https://peps.python.org/pep-0702/

At first glance, this PEP is... confusing. I haven't read it fully, but it does the opposite of #36 -- i.e. it's a thing that seems to only help for calling functions, instantiating classes, etc.

So users using deprecated things by simply accessing them will get no warning?

But we should at least integrate with it in the limited cases where that overlaps.