.Net: Introduce Grouding with Google Search configuration

[scherervictor]

Motivation and Context

This PR is enables the configuration of Grouding with Google Search in the Gemini API.

Description

• Added grounding_config that receives google_search object
• Implemented a validation to add googleSearch under tools object if configured.
• Adding proper deserialization of possible values returning after using Grouding.
• Included unit tests to validate the functionality for GroudingConfig and GoogleSearch.

Contribution Checklist

• [Y] The code builds clean without any errors or warnings
• [Y] The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• [Y] All unit tests pass, and I have added new tests where possible
• [Y] I didn't break anyone :smile:

Implements #11735

[scherervictor]

@microsoft-github-policy-service agree

[MarioGK]

Are there any blockers to merge this?

[PhilippCh]

Any update on this? It's been a requested feature since at least 2024 and has been requiring a review for over two months..

[wilhelmberghammer]

This would be really useful, any news on that?