Fix serialization (#94096)
We now always have a `__getstate__`/`__setstate__` pair AND the `__dict__` attribute is lazily initialized. So we need to support that in our serialization code.
A quick audit of the rest doesn't look like the new `__getstate__` is too problematic. But maybe the test suite will bring more things to light.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94096
Approved by: https://github.com/ezyang, https://github.com/malfet
