FSDP x TP Saving / Loading, Optimizer (#49256)
* Revert "refactor: restore optimizer changes for stacking"
This reverts commit e4b7ba0e9bbf22ed5144cf4271f29fa42621224e.
* fix: update guards as they now return booleans
* feat: use reverse logic in load_optimizer_distributed
* refactor: rename helper function
* style: ruff
