Move TF building to an actual build() method (#23760)

* A fun new PR where I break the entire codebase again

* A fun new PR where I break the entire codebase again

* Handle cross-attention

* Move calls to model(model.dummy_inputs) to the new build() method

* Seeing what fails with the build context thing

* make fix-copies

* Let's see what fails with new build methods

* Fix the pytorch crossload build calls

* Fix the overridden build methods in vision_text_dual_encoder

* Make sure all our build methods set self.built or call super().build(), which also sets it

* make fix-copies

* Remove finished TODO

* Tentatively remove unneeded (?) line

* Transpose b in deberta correctly and remove unused threading local

* Get rid of build_with_dummies and all it stands for

* Rollback some changes to TF-PT crossloading

* Correctly call super().build()

tests/models/opt/test_modeling_tf_opt.py

@@ -194,7 +194,7 @@ class TFOPTModelTest(TFModelTesterMixin, PipelineTesterMixin, unittest.TestCase)
             else:
                 # Here we build the word embeddings weights if not exists.
                 # And then we retry to get the attribute once built.
-                model(model.dummy_inputs)
+                model.build()
                 if hasattr(embedding_layer, "weight"):
                     return embedding_layer.weight
                 else: