Support extra tools argument for pandas agent toolkit (#11040)

**Description** 

We support adding new tools in some toolkits already like the [SQLAgent
toolkit](https://github.com/langchain-ai/langchain/blob/master/libs/langchain/langchain/agents/agent_toolkits/sql/base.py#L27).

Related
[SO](https://stackoverflow.com/questions/76583163/are-langchain-toolkits-able-to-be-modified-can-we-add-tools-to-a-pandas-datafra)
thread
This replicates the same functionality here, so users can add custom
bespoke tools.

libs/langchain/langchain/agents/agent_toolkits/pandas/base.py

@@ -1,5 +1,5 @@
 """Agent for working with pandas objects."""
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Sequence, Tuple
 
 from langchain.agents.agent import AgentExecutor, BaseSingleActionAgent
 from langchain.agents.agent_toolkits.pandas.prompt import (
@@ -21,6 +21,7 @@ from langchain.chains.llm import LLMChain
 from langchain.schema import BasePromptTemplate
 from langchain.schema.language_model import BaseLanguageModel
 from langchain.schema.messages import SystemMessage
+from langchain.tools import BaseTool
 from langchain.tools.python.tool import PythonAstREPLTool
 
 
@@ -280,12 +281,13 @@ def create_pandas_dataframe_agent(
     agent_executor_kwargs: Optional[Dict[str, Any]] = None,
     include_df_in_prompt: Optional[bool] = True,
     number_of_head_rows: int = 5,
+    extra_tools: Sequence[BaseTool] = (),
     **kwargs: Dict[str, Any],
 ) -> AgentExecutor:
     """Construct a pandas agent from an LLM and dataframe."""
     agent: BaseSingleActionAgent
     if agent_type == AgentType.ZERO_SHOT_REACT_DESCRIPTION:
-        prompt, tools = _get_prompt_and_tools(
+        prompt, base_tools = _get_prompt_and_tools(
             df,
             prefix=prefix,
             suffix=suffix,
@@ -293,6 +295,7 @@ def create_pandas_dataframe_agent(
             include_df_in_prompt=include_df_in_prompt,
             number_of_head_rows=number_of_head_rows,
         )
+        tools = base_tools + list(extra_tools)
         llm_chain = LLMChain(
             llm=llm,
             prompt=prompt,
@@ -306,7 +309,7 @@ def create_pandas_dataframe_agent(
             **kwargs,
         )
     elif agent_type == AgentType.OPENAI_FUNCTIONS:
-        _prompt, tools = _get_functions_prompt_and_tools(
+        _prompt, base_tools = _get_functions_prompt_and_tools(
             df,
             prefix=prefix,
             suffix=suffix,
@@ -314,6 +317,7 @@ def create_pandas_dataframe_agent(
             include_df_in_prompt=include_df_in_prompt,
             number_of_head_rows=number_of_head_rows,
         )
+        tools = base_tools + list(extra_tools)
         agent = OpenAIFunctionsAgent(
             llm=llm,
             prompt=_prompt,