TF generate refactor - Greedy Search (#15562)

* TF generate start refactor

* Add tf tests for sample generate

* re-organize

* boom boom

* Apply suggestions from code review

* re-add

* add all code

* make random greedy pass

* make encoder-decoder random work

* further improvements

* delete bogus file

* make gpt2 and t5 tests work

* finish logits tests

* correct logits processors

* correct past / encoder_outputs drama

* refactor some methods

* another fix

* refactor shape_list

* fix more shape list

* import shape
_list

* finish docs

* fix imports

* make style

* correct tf utils

* Fix TFRag as well

* Apply Lysandre's and Sylvais suggestions

* Update tests/test_generation_tf_logits_process.py

Co-authored-by: Matt <Rocketknight1@users.noreply.github.com>

* Update src/transformers/tf_utils.py

Co-authored-by: Matt <Rocketknight1@users.noreply.github.com>

* remove cpu according to gante

* correct logit processor

Co-authored-by: Matt <Rocketknight1@users.noreply.github.com>

tests/test_modeling_tf_common.py

@@ -955,7 +955,7 @@ class TFModelTesterMixin:
                 # Models with non-text inputs won't work here; num_return_sequences = 1
                 self._check_generated_ids(model.generate(do_sample=True, max_length=5))
 
-            with self.assertRaises(AssertionError):
+            with self.assertRaises(ValueError):
                 # generating multiple sequences when no beam search generation
                 # is not allowed as it would always generate the same sequences
                 model.generate(input_ids, do_sample=False, num_return_sequences=2)