google_ai: Parse thought parts in Gemini responses (#31925)

Fixes thinking Gemini models.

Closes #31902

Release Notes:

- Updated Google Gemini client to match the latest API
3077abf9cfFernando Freire committed on 6/3/2025, 10:37:06 AM· committed by GitHubparent07dab4e
2 files changedLine totals unavailable