`cubeb` audio backend improvements

[orottier]

• Fix occasional segfaults when interacting with the stream (suspend, resume, get latency)
• Support other output channel configs than STEREO
• Validate 4.1 output and other number of speakers
• Support other input channel configs than STEREO
• Setup a single stream for both input and output handling (currently two streams are used, leading to time drifts)
• What if hardware does not support SampleFormat::Float32LE?

[orottier]

A solution for the segfaults could be to run the rust implementation of the audiounit backend: mozilla/cubeb-rs#75 (comment)