add support for optional arguments on ai_callable functions

[theomonnom]

Example:

    @llm.ai_callable(description="Update the user information")
    async def update_user_info(
        self,
        name: str | None = None
        email: str | None = None
    ):
        ...

[changeset-bot]

🦋 Changeset detected

Latest commit: 6c8c0a1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
livekit-agents	Patch

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