Add --no-audio support to VM spec (#460)

tart run supports --no-audio to disable host audio pass-through, but
there was no way to request it through a VM's spec - Headless, Nested,
and Suspendable all have a flag/field but audio didn't. Useful on
headless hosts with no audio hardware, where audio pass-through can
make guest CoreAudio depend on host audio services that don't exist.

api/openapi.yaml

@@ -743,6 +743,10 @@ components:
           type: boolean
           description: Enable nested virtualization
           default: false
+        noAudio:
+          type: boolean
+          description: Whether to disable audio pass-through to the host
+          default: false
         username:
           type: string
           description: SSH username to use when connecting to a VM