Add support for thought field in AzureAIChatCompletionClient

[jay-thakur]

Why are these changes needed?

added support for the thought process in tool calls for OpenAIChatCompletionClient, allowing additional text produced by a model alongside tool calls to be preserved in the thought field of CreateResult. This PR extends the same functionality to AzureAIChatCompletionClient for consistency across model clients.

Related issue number

#5650

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.75%. Comparing base (47ffacc) to head (50bee50).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6062      +/-   ##
==========================================
+ Coverage   76.65%   76.75%   +0.10%     
==========================================
  Files         191      191              
  Lines       13222    13226       +4     
==========================================
+ Hits        10135    10152      +17     
+ Misses       3087     3074      -13     

Flag	Coverage Δ
unittests	76.75% <100.00%> (+0.10%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[ekzhu]

Could you add a unit test similar to the one for testing thought field OpenAIChatCompletionClient?