[quant][graphmode][fx][refactor] Remove save_state and restore_state from Quantizer class (#59035)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59035
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: D28724872
fbshipit-source-id: d32752c635917c9820e5e7cc414ba9d48a258a19
