feat(live): support live for gemini-3.1-flash-live-preview model

[zigzago]

Problem:
adk-java does not support gemini-3.1-flash-live-preview model

Solution:
Ported from Python google/adk-python@8082893

Testing Plan

Tested the bidi demo with new model and the 2.5 model

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Manual End-to-End (E2E) Tests:

bidi demo works with gemini-3.1-flash-live-preview model

Checklist

• I have read the CONTRIBUTING.md document.
• My pull request contains a single commit.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

[hemasekhar-p]

Hi @zigzago, thank you for your contribution! We appreciate you taking the time to submit this pull request. Could you please resolve the merge conflicts so we can move forward with the review?