[DDP] Log if graph is static at end of training (#61871)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61871
When set_static_graph=False, the only type of dynamism we really
support in DDP is dynamic set of unused parameters which must be explicitly
enabled with find_unused_parameters=True. Although, some workflows have static
set of unused parameters, would be good to detect and add this to logging to
identify workflows that are candidates for static graph optimization.
ghstack-source-id: 134371429
Test Plan: CI
Reviewed By: zhaojuanmao
Differential Revision: D29773962
fbshipit-source-id: 1f741984c6e6f8e3e55cf69ca719b1e25a485b13
