spa: send control sequences in adapter-control example for fade in/out effects

The adapter-control example now sends control sequences that changes the volume
every specific amount of samples, this produces a fade in/out effect when
running, and allow us to make sure the channelmix control port works correcly.
2 jobs for channelmix-control-port in 1 minute and 27 seconds
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passed build-container #1768089

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passed build #1768090

00:01:05