Add TF implementation of GPT-J (#15623)

* Initial commit

* Add TFGPTJModel

* Fix a forward pass

* Add TFGPTJCausalLM

* Add TFGPTJForSequenceClassification

* Add TFGPTJForQuestionAnswering

* Fix docs

* Deal with TF dynamic shapes

* Add Loss parents to models

* Adjust split and merge heads to handle 4 and 5-dim tensors

* Update outputs for @tooslow tests

docs/source/model_doc/gptj.mdx

@@ -130,6 +130,26 @@ model.
 [[autodoc]] GPTJForQuestionAnswering
     - forward
 
+## TFGPTJModel
+
+[[autodoc]] TFGPTJModel
+    - call
+
+## TFGPTJForCausalLM
+
+[[autodoc]] TFGPTJForCausalLM
+    - call
+
+## TFGPTJForSequenceClassification
+
+[[autodoc]] TFGPTJForSequenceClassification
+    - call
+
+## TFGPTJForQuestionAnswering
+
+[[autodoc]] TFGPTJForQuestionAnswering
+    - call
+
 ## FlaxGPTJModel
 
 [[autodoc]] FlaxGPTJModel