Multi channel audio merging (#320)

* Allow developers to merge audio channels.
Developers can pick any individual audio channel, sum all channels, or sum specific channels.
Set channelMode in WhisperKitConfig and pass the AudioInputConfig.

* Cleanup and formatting.

* Added helper function to read audio channel into buffer.
This maintains the integrity of the file.
Changed unit test to use 10 mins of audio.

* Format

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Co-authored-by: Rik Basu <rikbasu@Riks-MacBook-Pro-2.local>
Co-authored-by: ZachNagengast <znagengast@gmail.com>