Extend 2Dim embedding bag benchmarking to include 3Dim benchmarks (#64647)

Extend 2Dim embedding bag benchmarking to include 3Dim benchmarks (#64647)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64647

Add support for benchmarking of 8 bit quantizations of N-D batched embeddings. Currently only works for 3Dim embeddings and still requires thought on ramping up from 3Dim to NDim.

Test Plan: ```buck run //caffe2/benchmarks/operator_benchmark/pt:qembedding_pack_test```

Reviewed By: jingsh

Differential Revision: D30770085

fbshipit-source-id: 26659020f3458991592065a05366bde0f060494e