[quant][embedding qat] Support Embedding QAT via FX API (#68296)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68296
Support QAT workflow by using torch.fx QAT API. e.g. `prepare_qat_fx` and `convert_fx`.
Test Plan:
`pytest test/quantization/fx/test_quantize_fx.py -v -k "test_qat_embedding_linear"`
Imported from OSS
Reviewed By: jingsh, supriyar
Differential Revision: D32404517
fbshipit-source-id: 0484df8c826b823b60dfecd9def77bf8cffe0527
