autogen subpackage

[sonichi]

Why are these changes needed?

1. Create an autogen subpackage to facilitate the generative ai automation. Add utils for code and math tasks.
2. Update AOAI version.
3. Skip stop if None.

Related issue number

#949

Checks

• I've used pre-commit to lint the changes in this PR, or I've made sure lint with flake8 output is two 0s.
• I've included any doc changes needed for https://microsoft.github.io/FLAML/. See https://microsoft.github.io/FLAML/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.

[liususan091219]

Are these post processing steps required for the comparison between ground truth and the prediction?

[liususan091219]

What's the plan for autogen?

[sonichi]

What's the plan for autogen?

The plan is open for discussion. Suggestions are appreciated.