[quant][fx][refactor] Move ObservationType to backend_config.py (#83368)
Summary:
Now we have a separate file to define BackendConfig related classes, we can move ObservationType to that file as well
Test Plan:
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
python test/test_quantization.py TestQuantizeFxModels
Reviewers:
Subscribers:
Tasks:
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Pull Request resolved: https://github.com/pytorch/pytorch/pull/83368
Approved by: https://github.com/andrewor14
