pytorch

1ba4e3c7 - [FSDP][BE] Remove `_module_to_handles`, `HandleConfig`; use term "fqn"; clarify docs (#90840)

[FSDP][BE] Remove `_module_to_handles`, `HandleConfig`; use term "fqn"; clarify docs (#90840) This PR - Removes `_module_to_handles` since it is no longer used. We instead use `_comm_module_to_handles`. - Removes `HandleConfig` and stores its fields directly as attributes on `FlatParamHandle`. - Uses the term `fqn`/`fqns` uniformly in `flat_param.py` instead of `prefixed_param_name` / `prefixed_param_names`. - Clarifies some documentation. I am including all of these BE items in the same PR to save CI. Pull Request resolved: https://github.com/pytorch/pytorch/pull/90840 Approved by: https://github.com/rohan-varma