Add EXAONE 4.0 model (#39129)

* Add EXAONE 4.0 model

* Refactor EXAONE 4.0 modeling code

* Fix cache slicing on SWA + FA2

* Fix cache slicing on FA2 + HybridCache

* Update EXAONE 4.0 modeling code for main branch

* Update o_proj for asymmetric projection

* Address PR feedback

* Add EXAONE 4.0 docs

* Update EXAONE 4.0 modeling code for main branch

* update

* fix updates

* updates

* fix

* fix

* fix

---------

Co-authored-by: Arthur <arthur.zucker@gmail.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

utils/check_docstrings.py

@@ -79,6 +79,7 @@ ALWAYS_OVERRIDE = ["labels"]
 # docstrings instead. If formatting should be ignored for the docstring, you can put a comment # no-format on the
 # line before the docstring.
 OBJECTS_TO_IGNORE = [
+    "Exaone4Config",
     "SmolLM3Config",
     "Gemma3nVisionConfig",
     "Llama4Processor",