[RoPE] abstract dynamic RoPE update under a decorator ✨ (#37249)

* dynamic rope decorator

* longrope; shorter fwd pass

* propper docstring

* make fixup

utils/check_repo.py

@@ -1083,8 +1083,7 @@ def check_all_objects_are_documented():
     undocumented_objs = [c for c in objects if c not in documented_objs and not ignore_undocumented(c)]
     if len(undocumented_objs) > 0:
         raise Exception(
-            "The following objects are in the public init so should be documented:\n - "
-            + "\n - ".join(undocumented_objs)
+            "The following objects are in the public init, but not in the docs:\n - " + "\n - ".join(undocumented_objs)
         )
     check_model_type_doc_match()
     check_public_method_exists(documented_methods_map)