Bing grounding citations (#6370)

Adding support for Bing grounding citations to the AzureAIAgent.

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## Why are these changes needed?

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## Related issue number

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## Checks

- [X] 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.
- [X] I've added tests (if relevant) corresponding to the changes
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Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>
Co-authored-by: Dheeraj Bandaru <BandaruDheeraj@users.noreply.github.com>