Refactor audio code out of bootanimation_main.

So it can be shared with the iot/ variant I refactored it into the
audioplay.h file. This keeps all of the audio code local, we could hide
the functions and only expose the callback but that would make testing
harder.

Test: Ran a bootanimation.zip with audio.wav on Marlin, works as expected.
Bug: 67051984
Change-Id: Ie31dc5f2cfaad5bb23134ef81be712afa6b3cd6f