SK assistant for agentchat

[lspinheiro]

Why are these changes needed?

Adds an agentchat chat agent based on semantic kernel that allows the integration of most of the semantic kernel ecosystem.

Still need to update message conversion to handle non-text types, add docstring, etc. But the basics are thre.

Related issue number

Closes #4741

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

Attention: Patch coverage is 96.84211% with 3 lines in your changes missing coverage. Please review.

Project coverage is 70.30%. Comparing base (55e929d) to head (3debf1c).

Files with missing lines	Patch %	Lines
..._ext/agents/semantic_kernel/_sk_assistant_agent.py	96.77%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5134      +/-   ##
==========================================
+ Coverage   70.08%   70.30%   +0.21%     
==========================================
  Files         179      181       +2     
  Lines       11620    11715      +95     
==========================================
+ Hits         8144     8236      +92     
- Misses       3476     3479       +3     

Flag	Coverage Δ
unittests	70.30% <96.84%> (+0.21%)	⬆️

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[ekzhu]

For SK's list of responses, are they separate messages or a single message? Is it possible for this to contain messages that may contain tool calls?

[lspinheiro]

It returns a list

    async def get_chat_message_contents(
        self,
        chat_history: "ChatHistory",
        settings: "PromptExecutionSettings",
        **kwargs: Any,
    ) -> list["ChatMessageContent"]:

But it can return tool calls, it is a good catch. This depends on the configuration of the prompt settings. In the model adapter we are forcing semantic kernel to return tool calls to keep the same contract of the chat completion client. Here in the sample I'm using semantic kernel to automatically execute the function but this is not being forced in the configuration. Do you think we should force it or allow it to return tool calls? We may need to be more explicit about this behavior in the docs and maybe log some warnings