feat: add support for audioTimestamp in GenerationConfig

[jayhickey]

Adding support for the audioTimestamp to the GenerationConfig. This is already supported in the Python SDK and the documentation references it:

The following shows you how to use an audio file to transcribe an interview. To enable timestamp understanding for audio-only files, enable the audioTimestamp parameter in GenerationConfig.

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[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
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[timconnorz]

Would love to see this merged! we really need it!!

[jayhickey]

Could I get some eyes on this please? 🙏

cc @pavelgj @yyyu-google @happy-qiao if any of you are able to review?