[Docs] Model_doc structure/clarity improvements (#26876)

* first batch of structure improvements for model_docs

* second batch of structure improvements for model_docs

* more structure improvements for model_docs

* more structure improvements for model_docs

* structure improvements for cv model_docs

* more structural refactoring

* addressed feedback about image processors

docs/source/en/model_doc/cpm.md

@@ -37,7 +37,14 @@ NLP tasks in the settings of few-shot (even zero-shot) learning.*
 This model was contributed by [canwenxu](https://huggingface.co/canwenxu). The original implementation can be found
 here: https://github.com/TsinghuaAI/CPM-Generate
 
-Note: We only have a tokenizer here, since the model architecture is the same as GPT-2.
+
+<Tip>
+
+CPM's architecture is the same as GPT-2, except for tokenization method. Refer to [GPT-2 documentation](gpt2) for 
+API reference information.  
+
+</Tip>
+
 
 ## CpmTokenizer