Paligemma causal attention mask (#30967)

* PaliGemma working causal attention

* Formatting

* Style

* Docstrings + remove commented code

* Update docstring for PaliGemma Config

* PaliGemma - add separator ind to model/labels

* Refactor + docstring paligemma processor method

* Style

* return token type ids when tokenizing labels

* use token type ids when building causal mask

* add token type ids to tester

* remove separator from config

* fix style

* don't ignore separator

* add processor documentation

* simplify tokenization

* fix causal mask

* style

* fix label propagation, revert suffix naming

* fix style

* fix labels tokenization

* [run-slow]paligemma

* add eos if suffixes are present

* [run-slow]paligemma

* [run-slow]paligemma

* add misssing tokens to fast version

* Apply suggestions from code review

Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* fix style

* [run-slow]paligemma

---------

Co-authored-by: Peter Robicheaux <peter@roboflow.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

tests/models/paligemma/test_modeling_paligemma.py

@@ -163,6 +163,8 @@ class PaliGemmaVisionText2TextModelTester:
             "pixel_values": pixel_values,
             "input_ids": input_ids,
             "attention_mask": attention_mask,
+            "labels": input_ids,
+            "token_type_ids": torch.zeros_like(input_ids),
         }
         return config, inputs_dict