Update and expose ZeroRedundancyOptimizer docs (#52937)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/52937
Test Plan: Imported from OSS
Reviewed By: blefaudeux
Differential Revision: D26696938
Pulled By: mrshenli
fbshipit-source-id: dafb00e5c9f0c0c602f471fdcb6416bde74f806b
