Add support for XLM-R XL and XXL models by modeling_xlm_roberta_xl.py (#13727)

* add xlm roberta xl

* add convert xlm xl fairseq checkpoint to pytorch

* fix init and documents for xlm-roberta-xl

* fix indention

* add test for XLM-R xl,xxl

* fix model hub name

* fix some stuff

* up

* correct init

* fix more

* fix as suggestions

* add torch_device

* fix default values of doc strings

* fix leftovers

* merge to master

* up

* correct hub names

* fix docs

* fix model

* up

* finalize

* last fix

* Apply suggestions from code review

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* add copied from

* make style

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

docs/source/_toctree.yml

@@ -312,6 +312,8 @@
       title: XLM-ProphetNet
     - local: model_doc/xlm-roberta
       title: XLM-RoBERTa
+    - local: model_doc/xlm-roberta-xl
+      title: XLM-RoBERTa-XL
     - local: model_doc/xlnet
       title: XLNet
     - local: model_doc/xlsr_wav2vec2