Follow up on https://github.com/zed-industries/zed/pull/37786

adds conditional cmp removing use of libwebrtc on windows/freebsd

They cant compile livekit yet. This removes microphone and echo
cancellation on those platforms however they can not join calls due to
the same cause so it does not matter.

Documentation and error handing improvements

Release Notes:

- N/A

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Co-authored-by: Richard <richard@zed.dev>