Adding learning rate schedulers to C++ API (#52268)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/50577
Learning rate schedulers had not yet been implemented for the C++ API.
This pull request introduces the learning rate scheduler base class and the StepLR subclass. Furthermore, it modifies the existing OptimizerOptions such that the learning rate scheduler can modify the learning rate.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52268
Reviewed By: mrshenli
Differential Revision: D26818387
Pulled By: glaringlee
fbshipit-source-id: 2b28024a8ea7081947c77374d6d643fdaa7174c1
