Adding support for lowering 4Bit EmbeddingBag Operator (#5806)
Summary:
Pull Request resolved: https://github.com/pytorch/glow/pull/5806
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64001
Add 4 bit embeddingbag operator in acc_ops.
Test Plan: Let CI run.
Reviewed By: jfix71
Differential Revision: D30532824
fbshipit-source-id: bf476c9710477792aae202dacf64e23539c33bd9
