Lint Python notebooks with ruff. (#12677)

The new ruff version fixed the blocking bugs, and I was able to fairly
easily us to a passing state: ruff fixed some issues on its own, I fixed
a handful by hand, and I added a list of narrowly-targeted exclusions
for files that are currently failing ruff rules that we probably should
look into eventually.

I went pretty lenient on the docs / cookbooks rules, allowing dead code
and such things. Perhaps in the future we may want to tighten the rules
further, but this is already a good set of checks that found real issues
and will prevent them going forward.

cookbook/rewrite.ipynb

@@ -31,12 +31,10 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from operator import itemgetter\n",
-    "\n",
     "from langchain.prompts import ChatPromptTemplate\n",
     "from langchain.chat_models import ChatOpenAI\n",
     "from langchain.schema.output_parser import StrOutputParser\n",
-    "from langchain.schema.runnable import RunnablePassthrough, RunnableLambda\n",
+    "from langchain.schema.runnable import RunnablePassthrough\n",
     "from langchain.utilities import DuckDuckGoSearchAPIWrapper"
    ]
   },