log more OOM sites (#893)
log more OOM sites (#893)

Summary:
- Adds memory summary logging to validation and optimization steps.
- Clarifies in the logging that optimization OOMs are not recoverable.
Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/893

Differential Revision: D18110763

Pulled By: jma127

fbshipit-source-id: 49340e611169c606ab9c991265167a79f51846e6

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq