Feat/elevenlabs live

[stepacool]

Why are these changes needed?

Issue was open (#3039)
11labs is one of the best/main voice providers out there.

Changes are the implementation of Elevenlabs STT/TTS within the current ag2's architecture of voice - meaning no VAD/turn taking in Pipe/Cascade. For that reason, streaming of STT is not implemented(doesn't align with the current agent/voice/pipe implementation, no support for interruptions etc.)

But added support

Related issue number

Closes #3039

Checks

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• [y] I've added tests (if relevant) corresponding to the changes introduced in this PR.
• [y] I've made sure all auto checks have passed.

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• [y] I understand the changes in this PR and can explain them in my own words.
• [y] I have verified that the PR description accurately reflects the actual diff.
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