Uniformize kwargs for Pixtral processor (#33521)

* add uniformized pixtral and kwargs

* update doc

* fix _validate_images_text_input_order

* nit

tests/test_processing_common.py

@@ -64,6 +64,8 @@ class ProcessorTesterMixin:
         component = component_class.from_pretrained(self.tmpdirname, **kwargs)  # noqa
         if attribute == "tokenizer" and not component.pad_token:
             component.pad_token = "[TEST_PAD]"
+            if component.pad_token_id is None:
+                component.pad_token_id = 0
 
         return component