libobs/media-io: Clean surround API

(also modifies obs-ffmpeg, audio-monitoring, win-wasapi, decklink,
obs-outputs)

Removes speaker layouts which are not exposed in UI.  The speaker
layouts selectable by users in the UI are the most common ones.  It is
not necessary to keep other layouts.  (This basically removes
5POINT1_SURROUND, 7POINT1_SURROUND, SURROUND =3.0).
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