[FEATURE] use axfer w/ timer-based scheduling instead of aplay w/ interrupts #932

Both PulseAudio and PipeWire use timer-based scheduling, instead of interrupt-based scheduling.
This is a 12+ year concept that we've implemented for a while, see
http://0pointer.de/blog/projects/pulse-glitch-free.html

We should have a test where this mode is used. axfer provides similar capabilities to aplay but allows for timer-based scheduling.