Add support to declare imports for code agent

[JasonZhu1313]

What does this PR do?

Collected suggestions and guidance from @aymeric-roucher!

Add support for declaring a list of available packages to import for the code agent. Previously, the code agent was limited to a fixed list of packages, which restricted its ability to utilize a wide range of Python's utilities and functionalities. By providing this import list explicitly, we aim to enable the model to leverage the provided packages.

List of changes:

• Add "You can use imports in your code, but only from the following list of modules: <<authorized_imports>>" in prompt
• Add functions to render the prompt with authorized import list provided by users.
• Fix a bug in test, the test is meant to add FinalAnswer in toolset but it added two duplicated PythonInterpreter tools.
• Added tests for updating prompt in python interpreter tool.
• Replaced *tools* in DEFAULT_REACT_CODE_SYSTEM_PROMPT with <<tool_names>> which will later be replaced with a list of tool names to confine model on a list of possible tools it can invoke.
• Allow a reduction of parsing errors by adding exception handling blocks for _, code_action = self.extract_action(llm_output=llm_output, split_token="Code:") and rationale, raw_code_action = self.extract_action(llm_output=llm_output, split_token="Code:")

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[aymeric-roucher]

@JasonZhu1313 you can check failing style tests here

[JasonZhu1313]

@JasonZhu1313 you can check failing style tests here

Done thanks!

[aymeric-roucher]

Seems all good to me, thanks a lot @JasonZhu1313! @LysandreJik do you want to have a double check?

[LysandreJik]

Ok, sounds good

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