Add GPT2ForTokenClassification (#13290)
* Add GPT2ForTokenClassification
* Fix dropout exception for GPT2 NER
* Remove sequence label in test
* Change TokenClassifierOutput to TokenClassifierOutputWithPast
* Fix for black formatter
* Remove dummy
* Update docs for GPT2ForTokenClassification
* Fix check_inits ci fail
* Update dummy_pt_objects after make fix-copies
* Remove TokenClassifierOutputWithPast
* Fix tuple input issue
Co-authored-by: danielsejong55@gmail.com <danielsejong55@gmail.com>
