`PyType_Watch` does not report deallocations

[markshannon]

Bug report

Bug description:

The PyType_Watch function is used heavily in the JIT and we rely on it to deoptimize when a class changes.

However, it does not trigger the callback function when a class is deallocated
which can lead to the following situation.

• We have jitted code that depends on the state of a class.
• That code does a pointer comparison on the address of a watched class and then assumes that class to be identical to when the code was compiled.
• The class is deallocated
• Another, different class is allocated at the same address
• Crash and burn

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-149216: Notify type watchers on heap type deallocation #149236