Allow easy registration of custom attention functions (#36889)
* Update modeling_utils.py
* style
* Update modeling_utils.py
* Update modeling_utils.py
* Update modeling_utils.py
* Update modeling_utils.py
* Update modeling_utils.py
* Update modeling_utils.py
* add to init
* Update modeling_utils.py
* style
* update
* Update modeling_utils.py
* Update modeling_utils.py
* style
* Add some doc
* Update _toctree.yml
* readd it for tgi/vllm compat
* CIs
* CIs