Merge https://github.com/google/adk-python/pull/2212
This PR closes issue #2202
ADK was not parsing the required attribute when using LiteLLM, letting the LLM decide what is required vs not, not respecting function definitions.
## Test Plan
There's a fork of adk-python that is being running live for over 2 weeks in our production environment with millions of requests per day.
Below you can find a screenshot of the unit tests passing. I've also added one change to the test cases to cover this scenario
<img width="1904" height="483" alt="image" src="https://github.com/user-attachments/assets/5a6eb069-63ae-45a3-baca-6b01543f56fb" />
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/2212 from thiagosalvatore:main 7de4037d8016389313f3fb22df40c12bac578523
PiperOrigin-RevId: 797393698
Thiago SalvatoreandCopybara-Service