Use getDeviceIds function to list audio devices instead of relying on contiguous IDs

[EvergreenTheTree]

Fixes #8013

As of RtAudio 6.0.0 you cannot assume that devices will fall in the range [0, getDeviceCount() - 1]. Doing so will potentially cause errors or out of bounds array accesses depending on the platform.

I am not super familiar with this project, but as far as I can tell I couldn't find any documentation or example projects that would need to be updated as a result of this change. However, I do know of at least two projects (audiostellar and ofxPDSP) that make this assumption, so it is definitely worth noting in the change log.