[Caffe2] Add RMSNormOp (#44338)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44338
Add RMSNormOp in Caffe2
Test Plan: buck test mode/dev-nosan //caffe2/caffe2/python/operator_test:rms_norm_op_test
Reviewed By: houseroad
Differential Revision: D23546424
fbshipit-source-id: 8f3940a0bb42230bfa647dc66b5e359cc84491c6
