reland - ns for fx - stubs of the three APIs (compare weights, activations, activations with shadow) (#52302)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52302
Adds the basic functionality for the three Numeric Suite core APIs to work on FX models:
1. comparing weights
2. comparing activations, with same input fed to both models
3. comparing activations, with nodes of A shadowing nodes of B
Note: there are a lot of TODOs in the code, and some/most of the APIs and implementation details may change as we iterate. This is just the first PR.
Test Plan:
We have unit test coverage for all of the APIs, for now this is with toy models:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
```
Reviewed By: raghuramank100
Differential Revision: D26463013
Pulled By: vkuzo
fbshipit-source-id: e454115099ad18e4037d3c54986951cdffcab367
