fix(llms): improve the ernie chat model (#9289)

- Description: improve the ernie chat model.
   - fix missing kwargs to payload
   - new test cases
   - add some debug level log
   - improve description
- Issue: None
- Dependencies: None
- Tag maintainer: @baskaryan

docs/extras/integrations/chat/ernie.ipynb

@@ -6,7 +6,8 @@
    "source": [
     "# ERNIE-Bot Chat\n",
     "\n",
-    "This notebook covers how to get started with Ernie chat models."
+    "[ERNIE-Bot](https://cloud.baidu.com/doc/WENXINWORKSHOP/s/jlil56u11) is a large language model developed by Baidu, covering a huge amount of Chinese data.\n",
+    "This notebook covers how to get started with ErnieBot chat models."
    ]
   },
   {
@@ -16,7 +17,7 @@
    "outputs": [],
    "source": [
     "from langchain.chat_models import ErnieBotChat\n",
-    "from langchain.schema import AIMessage, HumanMessage, SystemMessage"
+    "from langchain.schema import HumanMessage"
    ]
   },
   {