[Python] Protect PyBuffer and NumPyBuffer destructors against interpreter finalization

[pitrou]

Describe the bug, including details regarding any error messages, version, and platform.

In #38637 we protected the OwnedRef and OwnedRefNoGIL destructors against being called when the Python interpreter is being finalized, but we didn't address other classes with custom destructors, such as PyBuffer and NumPyBuffer.

Component(s)

Python