[dist_optim] add distributed functional RMSprop optimizer (#50619)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50619
Add TorchScript compatible RMSprop functional optimizer to distributed optimizer
Test Plan: Imported from OSS
Reviewed By: rohan-varma
Differential Revision: D25932775
Pulled By: wanchaol
fbshipit-source-id: bd4854f9f95a740e02a1bebe24f780488460ba4d
