Extend `nut-scanner` to suggest (commented-away) `allow_duplicates` when it may be applicable

[jimklimov]

Looking at issues like #2997 and #2791 and others that led up to introduction of the allow_duplicates option, it can be useful to see if scanning found several devices that would be indiscernible without options that we comment away by default (e.g. link-specific bus/busport/device), or perhaps even with these options (bad USB hub reporting all-zeroes?), and suggest the allow_duplicates option for end-user to consider. It has downsides, but may be better than nothing.