gh-95417: Add PyLong_FromUintptr_t and PyLong_AsUintptr_t

[arhadthedev]

This PR adds exports from the dll/so because all PyLong_* do so. However, if the core devs aren't against, I would prefer to transform them into inline macros (thus removing ABI churn and eliminating Misc/stable_abi.toml from the patch):

/* Include/longobject.h */

static uintptr_t
PyLong_AsUintptr_t(PyObject *vv)
{
    return (uintptr_t)PyLong_AsVoidPtr(vv);
}

static PyObject *
PyLong_FromUintptr_t(uintptr_t ival)
{
    return PyLong_FromVoidPtr((void *)ival);
}

Closes gh-95417.

cc @eryksun (who proposed to implement these functions).

• Issue: What way to choose to fix Warning: ULONG_PTR differs in levels of indirection from void * in AC-generated code? #95417

[arhadthedev]

cc @benjaminp (from the object model interest area) because the new functions convert to/from PyLong_Type.

[arhadthedev]

According to https://devguide.python.org/developer-workflow/c-api/#guidelines-for-adding-to-the-limited-api, addition of stable ABI requires long discussion. I'm not ready for this for the sake of a single use case so closing this PR.