Framework-agnostic `split_state_dict_into_shards` helper (#1938)
* Draft for a framework-agnostic 'split_state_dict_into_shards' helper
* refactor
* mee
* Fix storage id stuff + add tests
* add example
* docstrings
* fix tf
* deterministic tests
* 5GB shards
* import torch
* rename to split_state_dict_into_shards_factory
* fix
* docs/source/en/package_reference/serialization.md
* with docs