[quant] Add quantized Embedding module (#44208)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44208
Add quantized module in static quantization namespace. Embedding
quantization requires only weights to be quantized so it is static.
Internally it calls the embedding_bag_byte op with the offsets set corresponding to the
indices.
Future PR will move EmbeddingBag quantization from dynamic to static as well.
Test Plan:
python test/test_quantization.py test_embedding_api
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D23547384
fbshipit-source-id: eddc6fb144b4a771060e7bab5853656ccb4443f0
