Add support for specifying the languages to parse from the CodeExecutorAgent response

[Ethan0456]

Why are these changes needed?

The CodeExecutorAgent can generate code blocks in various programming languages, some of which may not be supported by the executor environment. Adding support for specifying languages to be parsed helps users ignore unnecessary code blocks, preventing potential execution errors.

Related issue number

Closes #6471

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md 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.

[Copilot]

Pull Request Overview

This PR lets users specify which languages to parse from CodeExecutorAgent responses to prevent executing unsupported code blocks.

• Added supported_languages to the agent config with a default of ["python", "bash"]
• Built a dynamic regex from supported_languages to filter Markdown code fences
• Persisted supported_languages in _to_config and _from_config

Comments suppressed due to low confidence (1)

python/packages/autogen-agentchat/src/autogen_agentchat/agents/_code_executor_agent.py:603

• No tests cover scenarios where code blocks have unsupported languages or no language tag. Add tests to verify these cases are properly ignored.

pattern = re.compile(rf"```(?:\s*({self._supported_languages_regex}))\n([\s\S]*?)```")

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.54%. Comparing base (03394a4) to head (3f8b673).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6592   +/-   ##
=======================================
  Coverage   79.53%   79.54%           
=======================================
  Files         225      225           
  Lines       16656    16662    +6     
=======================================
+ Hits        13248    13254    +6     
  Misses       3408     3408           

Flag	Coverage Δ
unittests	79.54% <100.00%> (+<0.01%)	⬆️

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