treatment: implement playing sound through yobert/alsa API rather than executing external cmd

[Trek Hopton]

Currently treatment (our speaker playing and monitoring software) plays sound by executing an external command, aplay or omxplayer. yobert/alsa is a go package for interacting with the linux ALSA library and should give us direct control over sound cards and playback/recording devices. We should utilise this so that we have more control in our program and do not have to deal with controlling the OS environment.

One benefit is that you can choose the sound card in code rather than having to set the default device in linux before running the program.