[Libosinfo] a couple meta-OS ideas

[Cole Robinson]

In virt-install we have the concept of a 'generic' osinfo ID. This is
basically a placeholder that means 'no OS implied defaults', when the
user doesn't specify an OS in any way. Internally we implement this by
wrapping every osinfo call and returning stub data if os == "generic".

Should we officially add something like this to osinfo-db? Besides
'generic' it could be named 'none' or 'unknown'. 'none' might make the
most sense from the API perspective but might send the wrong message in
a UI: the user will probably be installing an OS of some kind but it
might not be in the list or they just want to specifically opt out of
any defaults.

Regardless it's useful for apps to have some kind of blank os object to
interact with internally, rather than have to conditionalize the code
based on whether there was an explicit OS chosen. Maybe there's some
other strategy for dealing with this so suggestions welcome.

Somewhat related is the idea of having some kind of meta OS like
'linux2016' or similar. It's not a specific distro but instead tracks
devices and reasonable resource recommendations for common distros of
the time. The benefits would be 1) it gives users some reasonable target
to choose in a UI like virt-manager if their distro isn't listed, 2)
would give apps distro agnostic options to use as a default baseline.
I'm sure there's downsides though so again suggestions welcome. I've
mostly thought about this in the context of making
virt-manager/virt-install choose a virtio-using default OS in the future

Thanks,
Cole