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/vit/test_modeling_tf_vit.py

@@ -33,6 +33,7 @@ if is_tf_available():
     import tensorflow as tf
 
     from transformers import TFViTForImageClassification, TFViTModel
+    from transformers.modeling_tf_utils import keras
 
 
 if is_vision_available():
@@ -188,9 +189,9 @@ class TFViTModelTest(TFModelTesterMixin, PipelineTesterMixin, unittest.TestCase)
 
         for model_class in self.all_model_classes:
             model = model_class(config)
-            self.assertIsInstance(model.get_input_embeddings(), (tf.keras.layers.Layer))
+            self.assertIsInstance(model.get_input_embeddings(), (keras.layers.Layer))
             x = model.get_output_embeddings()
-            self.assertTrue(x is None or isinstance(x, tf.keras.layers.Layer))
+            self.assertTrue(x is None or isinstance(x, keras.layers.Layer))
 
     def test_forward_signature(self):
         config, _ = self.model_tester.prepare_config_and_inputs_for_common()