Cache: init empty cache when use_cache (#34274)

* fix

* fix tests

* fix copies

* add docs

* Revert "add docs"

This reverts commit 32d35634f12ba02781d2ebdee0c8dcfbe992a7b9.

* qwen move deltas

* mllama can potentiall fullgraph compile

* enable mllama compile and fix tests

* remove mllama fixes

tests/test_modeling_common.py

@@ -2343,7 +2343,8 @@ class ModelTesterMixin:
                             recursive_check(tuple_iterable_value, dict_iterable_value)
                     elif tuple_object is None:
                         return
-                    else:
+                    # model might return non-tensors objects (e.g. Cache class)
+                    elif isinstance(tuple_object, torch.Tensor):
                         self.assertTrue(
                             torch.allclose(
                                 set_nan_tensor_to_zero(tuple_object), set_nan_tensor_to_zero(dict_object), atol=1e-5