[FSDP][Docs] Make model/optim state dict configs visible in docs (#105848)
This closes https://github.com/pytorch/pytorch/issues/104717.
Rendered docs:
![Screenshot 2023-07-25 at 11 15 23 AM](https://github.com/pytorch/pytorch/assets/31054793/3c38166a-70c0-472c-805d-452d3bd9c700)
![Screenshot 2023-07-25 at 11 15 30 AM](https://github.com/pytorch/pytorch/assets/31054793/6d275d94-020a-44a2-a64c-0eeba083d47f)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105848
Approved by: https://github.com/rohan-varma