Fix Gemini function calling (#27905)

This seems to improve the performance of `gemini-2.5-pro-exp-03-25`
significantly.
We know define a single `Tool` that has multiple `FunctionDeclaration`s,
instead of defining multiple `Tool`s with a single
`FunctionDeclaration`.
Oddly enough the `flash` models seemed to work perfectly fine with the
multiple `Tool { ... }` definitions

Release Notes:

- N/A
b158ee60caBennet Bo Fenner committed on 4/2/2025, 10:35:17 AM· committed by GitHubparent9b7b4a9
1 file changedLine totals unavailable