Set new device_id when assigning PCI devices with VM settings

[marmarek]

How to file a helpful issue

The problem you're addressing (if any)

New devices API allows to identify devices not only with a "port id" (which is currently BDF for PCI), but also "device id" (vendor, product etc). qvm-pci tool uses that, but GUI settings don't.

The solution you'd like

Fill in device id too. This also means ensuring such assignment can is properly handled when opening the settings, and unassigning the device. Including the case when the device is not physically present anymore.

The value to a user, and who that user might be

More strict device assignments.

Completion criteria checklist

(This section is for developer use only. Please do not modify it.)

• fill in device_id when assigning
• ensure loading assignments with device_id works
• decide what to do about existing assignments without device_id (should those get device_id on save?)
• ensure non-present devices with device_id set are handled properly (should those get some metadata extracted from the device id, instead of just saying "unknown"?)
• same as above but when device with the same port-id is present but has different device_id - especially ensure the device_id won't get "updated"