GHSA-6JGW-RGMM-7CV6 PyO3 has a risk of use-after-free in `borrowed` reads from Python weak references

The family of functions to read "borrowed" values from Python weak references were fundamentally unsound, because the weak reference does itself not have ownership of the value. At any point the last strong reference could be cleared and the borrowed value would become dangling. In PyO3 0.22.4...