ns for fx: move it to top level file (#55060)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55060
Removes the previous iteration of Numeric Suite for FX graph mode
quantization, and moves the current iteration into the top level
file.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
python test/test_quantization.py TestFXGraphMatcher
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D27467725
fbshipit-source-id: 4c22b5a3221857231f9f59cf6d2908820e6a7f12
