Add config option to not alter default audio device

[scottpanton]

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Previous question on this issue here: https://github.com/orgs/LizardByte/discussions/261

On Windows, I'd like to be able to specify an audio sink to capture without having Sunshine alter the default. I want to be able to manage which audio is routed to this sink myself. In my case I'm using VoiceMeeter with the Steam virtual device as one of the outputs so I can manage what audio is sent there. Capturing the VoiceMeeter input device isn't a suitable solution as this will not capture audio from other sources.