[quant][fx] Using native backend_config_dict in fusion (#75378)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75378
Previously we are still relying on the registration mechnism and get the default fusion patterns that are registered,
now we have moved all registration to backend_config_dict we can get all fusion patterns just from backend_config_dict now.
This PR enables using native backend_config_dict everywhere in fusion when the backend_config_dict is None,
we'll do similar changes for prepare and convert in the future, to fully enable backend_config_dict in
quantization code base.
Test Plan:
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D35451962
fbshipit-source-id: 31d51850c669e061b67d6d9e0efec994f7ea79ed
(cherry picked from commit 60cc2dcadce705a923f9279465e3fb0e8fddad48)
