Add BlenderbotTokenizerFast (#13720)

* Add the support for the fast (rust) implementation of BlenbderbotTokenizer

* Fix a converter and a typo in a doc

* Apply the patil-suraj's suggestion

* (Nitpick) Fast tokenization -> Fast Tokenization in doc

* Apply the SaulLu's suggestion

* Apply Narsil's suggestion to fix test pipelines

* Add encoder_no_repeat_ngram_size according to the Narsil's suggestion

* Revert the last (unnecessary) commit

* Override pipeline config for Blenderbot to allow for larger pos. emb.

* make fix-copies

tests/test_modeling_blenderbot.py

@@ -137,6 +137,11 @@ class BlenderbotModelTester:
             pad_token_id=self.pad_token_id,
         )
 
+    def get_pipeline_config(self):
+        config = self.get_config()
+        config.max_position_embeddings = 100
+        return config
+
     def prepare_config_and_inputs_for_common(self):
         config, inputs_dict = self.prepare_config_and_inputs()
         return config, inputs_dict