[pytorch] Expose EmbeddingPackedParamsBase::unpack to Python (#88362)
Summary:
User can't call `.unpack()` when they have a quantized Embedding layer because `&EmbeddingPackedParamsBase::unpack` was never exposed to Python through pybind.
This diff fixes that.
Test Plan: CI
Reviewed By: jerryzh168
Differential Revision: D40606585
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88362
Approved by: https://github.com/jerryzh168
