[NamedOptimizer][2/N] Prepare the enablement of state_dict for FSDP (#91147)
1. Add param_group check logic and unit test
2. Remove unnecessary check for conditional param update
3. Return the param_group from the inner optimizer so that when param_group is None or not all params are specified, we still return the expected result.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91147
Approved by: https://github.com/fegin
