[DDP] logging improvements (#67059)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67059
Debugging some workflows, and sometimes the training does not finish
but I want to know whether the graph was not static. Also, log 0 for unused
parameter size if no unused params were found.
ghstack-source-id: 141428950
Test Plan: Ci
Reviewed By: mrshenli
Differential Revision: D31846669
fbshipit-source-id: 21763fcdc1b244ba829117da1f15b2271d966983
