track ddp API usage (#35837)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35837
track ddp API usage
ghstack-source-id: 101344592
Test Plan: check logging
Differential Revision: D20801983
fbshipit-source-id: f3d2e6ab5bde0b1320300d67a327f12ddb2c62e7
