MacOS: Integrate Custom Logic for key `Total Size`

[p-hebert]

The key Total Size provided by diskutil info -all can be used both as a replacement value for Disk Size (device) and Volume Total Space (volume). The target should be modified to dual and the logic of the mapper function altered to match the properties above. Attention should be given to whether or not custom logic is necessary in the cond operator in parseMacOSToProps.