[quant][graphmode][fx][refactor] Remove fold_weights from Quantizer class (#59036)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59036
To remove Quantizer class and split prepare and convert functions to different files
Test Plan:
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D28724862
fbshipit-source-id: 5900420127fcc14846bc34c9ac29ff7e6a703f1e
