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.