Add MVP model (#17787)

* Add MVP model

* Update README

* Remove useless module

* Update docs

* Fix bugs in tokenizer

* Remove useless test

* Remove useless module

* Update vocab

* Remove specifying

* Remove specifying

* Add #Copied ... statement

* Update paper link

* Remove useless TFMvp

* Add #Copied ... statement

* Fix style in test mvp model

* Fix some typos

* Fix properties of unset special tokens in non verbose mode

* Update paper link

* Update MVP doc

* Update MVP doc

* Fix README

* Fix typos in docs

* Update docs

docs/source/en/_toctree.yml

@@ -308,6 +308,8 @@
       title: MPNet
     - local: model_doc/mt5
       title: MT5
+    - local: model_doc/mvp
+      title: MVP
     - local: model_doc/nezha
       title: NEZHA
     - local: model_doc/nystromformer