[quant] Add torchbind support for embedding_bag packed weights (#42881)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42881
This enables serialization/de-serialization of embedding packed params using getstate/setstate calls.
Added version number to deal with changes to serialization formats in future.
This can be extended in the future to support 4-bit/2-bit once we add support for that.
Test Plan:
python test/test_quantization.py TestQuantizedEmbeddingBag
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D23070634
fbshipit-source-id: 2ca322ab998184c728be6836f9fd12cec98b2660
