fx quant: add more typehints (#48774)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48774
Adds some more typehints throughout `quantization/fx/quantize.py`.
More are needed, ran out of time for now, we can continue in
future PRs.
Test Plan:
```
mypy torch/quantization/fx/quantize.py
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D25295836
fbshipit-source-id: 4029aa8ea5b07ce9a57e4be6a66314d7a4e19585
