feat: change model patch structure

[sigoden]

-     patches: 
-       <regex>:                                      # The regex to match model names, e.g. '.*' 'gpt-4o' 'gpt-4o|gpt-4-.*'
-         chat_completions_body:                      # The JSON to be merged with the chat completions request body.
-           <json>
+     patch:                                          # Patch api request
+       chat_completions_body:                        
+         <regex>:                                    # The regex to match model names, e.g. '.*' 'gpt-4o' 'gpt-4o|gpt-4-.*'
+           <json>                                    # The JSON to be merged with the chat completions request body.