Add tf_keras imports to prepare for Keras 3 (#28588)

* Port core files + ESM (because ESM code is odd)

* Search-replace in modelling code

* Fix up transfo_xl as well

* Fix other core files + tests (still need to add correct import to tests)

* Fix cookiecutter

* make fixup, fix imports in some more core files

* Auto-add imports to tests

* Cleanup, add imports to sagemaker tests

* Use correct exception for importing tf_keras

* Fixes in modeling_tf_utils

* make fixup

* Correct version parsing code

* Ensure the pipeline tests correctly revert to float32 after each test

* Ensure the pipeline tests correctly revert to float32 after each test

* More tf.keras -> keras

* Add dtype cast

* Better imports of tf_keras

* Add a cast for tf.assign, just in case

* Fix callback imports

tests/models/efficientformer/test_modeling_tf_efficientformer.py

@@ -37,6 +37,7 @@ if is_tf_available():
         TFEfficientFormerForImageClassificationWithTeacher,
         TFEfficientFormerModel,
     )
+    from transformers.modeling_tf_utils import keras
     from transformers.models.efficientformer.modeling_tf_efficientformer import (
         TF_EFFICIENTFORMER_PRETRAINED_MODEL_ARCHIVE_LIST,
     )
@@ -355,7 +356,7 @@ class TFEfficientFormerModelTest(TFModelTesterMixin, PipelineTesterMixin, unitte
             # These are maximally general inputs for the model, with multiple None dimensions
             # Hopefully this will catch any conditionals that fail for flexible shapes
             functional_inputs = {
-                key: tf.keras.Input(shape=val.shape[1:], dtype=val.dtype, name=key)
+                key: keras.Input(shape=val.shape[1:], dtype=val.dtype, name=key)
                 for key, val in model.input_signature.items()
                 if key in model.dummy_inputs
             }