Upstream apply_optim_in_backward from TorchRec (#87397) (#88539)
Summary:
Upstreaming this as part of sharing common APIs. This is just a plain
move, any changes needed to support DDP / FSDP will come in follow up diffs.
Test Plan: CI
Reviewed By: zhaojuanmao
Differential Revision: D40564646
fbshipit-source-id: 619c434e02196812f8d4db1e40d07290e08b18f9
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88539
Approved by: https://github.com/awgu
