The use of `PyStackRef_AsPyObjectBorrow` makes it hard to track ownership of references, making analysis of escaping calls too difficult

The problem with PyStackRef_AsPyObjectBorrow is that it is not clear whether the reference is owned by the stack ref or the pointer.

Borrowing references across calls is fine but in less structured code, it is error prone and very hard to analyze.

The solution is change most, ideally all, uses of PyStackRef_AsPyObjectBorrow to PyStackRef_AsPyObjectSteal so that the ownership of the reference is clear.
E.g.

        inst(UNARY_NEGATIVE, (value -- res)) {
            PyObject *val_o = PyStackRef_AsPyObjectBorrow(value);
            PyObject *res_o = PyNumber_Negative(val_o);
            PyStackRef_CLOSE(value);
            ERROR_IF(res_o == NULL, error);
            res = PyStackRef_FromPyObjectSteal(res_o);
        }

would become:

        inst(UNARY_NEGATIVE, (value -- res)) {
            PyObject *val_o = PyStackRef_AsPyObjectSteal(value);
            PyObject *res_o = PyNumber_Negative(val_o);
            Py_DECREF(val_o);
            ERROR_IF(res_o == NULL, error);
            res = PyStackRef_FromPyObjectSteal(res_o);
        }

This ensures that during the escaping call to PyNumber_Negative, the reference to the value a PyObject *, so will not be reclaimed by the garbage collector.

Linked PRs

• gh-122037

Search the CPython source for uses of PyStackRef_AsPyObjectBorrow and review the PyStackRef_AsPyObjectSteal and PyStackRef_CLOSE ownership patterns shown in the issue. Determine which uses cross calls that can escape, then verify that the relevant references remain valid and ownership is explicit; compare the work with linked PR gh-122037.