[DDP] Log iteration in debug mode (#65770)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65770
This logging info is printed out in debug mode, make it log the
iteration as well for clarity.
ghstack-source-id: 139838595
Test Plan: CI
Reviewed By: zhaojuanmao, wayi1
Differential Revision: D31222132
fbshipit-source-id: 14519aae1ba0b2a35b4b962e7d1a957c9142c8f8
