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/convbert/test_modeling_tf_convbert.py

@@ -37,6 +37,7 @@ if is_tf_available():
         TFConvBertForTokenClassification,
         TFConvBertModel,
     )
+    from transformers.modeling_tf_utils import keras
 
 
 class TFConvBertModelTester:
@@ -306,7 +307,7 @@ class TFConvBertModelTest(TFModelTesterMixin, PipelineTesterMixin, unittest.Test
             with tempfile.TemporaryDirectory() as tmpdirname:
                 model.save_pretrained(tmpdirname, saved_model=True)
                 saved_model_dir = os.path.join(tmpdirname, "saved_model", "1")
-                model = tf.keras.models.load_model(saved_model_dir)
+                model = keras.models.load_model(saved_model_dir)
                 outputs = model(class_inputs_dict)
 
                 if self.is_encoder_decoder: