Improve mac-avcapture logging

Log messages are now prefixed with the source name to distinguish between
multiple sources
Refactor mac-avcapture cleanup and improve session init error handling
Move device handling in mac-avcapture to separate functions
Fix minor style-deviation in mac-avcapture
Improve preset selection robustness in mac-avcapture
Enable device selection for mac-avcapture
Add connect/disconnect handling for mac-avcapture