fake_quant: fix device affinity and buffer resizing for state_dict (#50868)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50868
Ensures that `FakeQuantize` respects device affinity when loading from
state_dict, and knows how to resize scale and zero_point values
(which is necessary for FQ classes wrapping per channel observers).
This is same as https://github.com/pytorch/pytorch/pull/44537, but for
`FakeQuantize`.
Test Plan:
```
python test/test_quantization.py TestObserver.test_state_dict_respects_device_affinity
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D25991570
fbshipit-source-id: 1193a6cd350bddabd625aafa0682e2e101223bb1
