docs: langchain-openai (#15513)

Updates docs and cookbooks to import ChatOpenAI, OpenAI, and OpenAI
Embeddings from `langchain_openai`

There are likely more

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

cookbook/multiagent_bidding.ipynb

@@ -33,7 +33,7 @@
     "    HumanMessage,\n",
     "    SystemMessage,\n",
     ")\n",
-    "from langchain_community.chat_models import ChatOpenAI"
+    "from langchain_openai import ChatOpenAI"
    ]
   },
   {