To add state dict and load_dict for Chained Scheduler (#65034)
Summary:
Adding state_dict() and load_state_dict() methods for Chained Scheduler
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65034
Reviewed By: prabhat00155, nateanl
Differential Revision: D30958207
Pulled By: datumbox
fbshipit-source-id: 1a587a330d34e0548e891a39f8fb5a3d251b71fa
