- on large recordings (e.g. radio transmissions), ffprobe might return number of hours which is too large for TimeSpan.Parse (exception: The TimeSpan string '149:07:50.911750' could not be parsed because at least one of the numeric components is out of range or contains too many digits.)
- use regex groups to extract components (hours/minutes/seconds/millis) then parse/create new timespan from that
- NOTICE: this will discard microseconds provided by ffprobe, not sure if this is significant
- ffprobe has inconsitencies with how it represents millisecond component. Sometimes it may return just `82` for 820 milliseconds, so padding with 0s is required on the left. Likewise, sometimes it might return microseconds past milliseconds (first 3 significant figures); this is currently discarded
- Added InternalsVisibleTo to help with unit testing *just* the duration parsing function
