Support T5 Generation (#3228)

* fix conflicts

* update bart max length test

* correct spelling mistakes

* implemented model specific encode function

* fix merge conflicts

* better naming

* save intermediate state -> need to rethink strucuture a bit

* leave tf problem as it is for now

* current version

* add layers.pop

* remove ipdb

* make style

* clean return cut decoding

* remove ipdbs

* Fix restoring layers in the decoders that doesnt exists.

* push good intermediate solution for now

* fix conflicts

* always good to refuse to merge conflicts when rebasing

* fix small bug

* improve function calls

* remove unused file

* add correct scope behavior for t5_generate

Co-authored-by: Morgan Funtowicz <funtowiczmo@gmail.com>

src/transformers/__init__.py

@@ -255,7 +255,7 @@ if is_torch_available():
     from .modeling_t5 import (
         T5PreTrainedModel,
         T5Model,
-        T5WithLMHeadModel,
+        T5ForConditionalGeneration,
         load_tf_weights_in_t5,
         T5_PRETRAINED_MODEL_ARCHIVE_MAP,
     )
@@ -444,7 +444,7 @@ if is_tf_available():
     from .modeling_tf_t5 import (
         TFT5PreTrainedModel,
         TFT5Model,
-        TFT5WithLMHeadModel,
+        TFT5ForConditionalGeneration,
         TF_T5_PRETRAINED_MODEL_ARCHIVE_MAP,
     )