Use OpenAI request ID for TTS emitter

[anishnag]

We use the OpenAI request ID for TTS instead of random UUID.

[github-actions[bot]]

:x: Invalid Changeset Format Detected

One or more changeset files in this PR have an invalid format. Please ensure they adhere to:

• Start with --- and include a closing --- on its own line.
• Each package line must be in the format: "package-name": patch|minor|major
• No duplicate package entries allowed.
• A non-empty change description must follow the front matter.

Error details: .github/next-release/changeset-de15f366.md: Failed to read file from git branch 'pr_head'.

[theomonnom]

Hey, I've been handling it inside this PR.

We changed the way we emit the synthesized audio, so it's much easier to do it (no need for asyncio primitives) https://github.com/livekit/agents/blob/285883ab07c0d5cc02d0e95212e46b04aadb0f24/livekit-plugins/livekit-plugins-openai/livekit/plugins/openai/tts.py#L200