[quant][fx] Use native backend_config_dict in prepare
Summary:
Previously we are still relying on the registration mechnism and get the default quantize handlers that are registered,
now we have moved all registration to backend_config_dict we can get all quant patterns just from backend_config_dict now.
This PR enables using native backend_config_dict everywhere in prepare when the backend_config_dict is None, we'll also
do similar changes in convert as well
Test Plan:
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
Summary:
Test Plan:
Reviewers:
Subscribers:
Tasks:
Tags:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75469
Approved by: https://github.com/vkuzo
