[quant][embedding qat] Re-Land Support Embedding QAT via FX API (#69333)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69333
Original PR reverted due to break with incompatible qengine on Mac OS, this diff fixes that.
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
Differential Revision: D32814827
fbshipit-source-id: f7a69d2b596f1276dc5860b397c5d5d07e5b9e16
