[FSDP][Wrap] ModuleWrapPolicy callable (#109117)
Makes ModuleWrapPolicy callable, in my case this is needed for
composition with or_policy. We should also make or_policy a public interface
IMO.
Differential Revision: [D49175112](https://our.internmc.facebook.com/intern/diff/D49175112/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/109117
Approved by: https://github.com/fegin
ghstack dependencies: #109116
