[FSDP][optim_state_dict][11/N] Let FSDP support NamedOptimizer/KeyedOptimizer when use_orig_params is False (#92184)
Current design of FSDP only support NamedOptimizer/KeyedOptimizer when use_orig_params is True this PR adds the support even if use_orig_params if False. This PR also adds the support for user-defined optimizer states -- states that are not associated with any particular parameters.
Differential Revision: [D42497416](https://our.internmc.facebook.com/intern/diff/D42497416/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/92184
Approved by: https://github.com/colin2328, https://github.com/rohan-varma
