PCI devices are now handled as DeviceInfo objects, not (string,name) tuples;
furthermore, a device that no longer exists in the system can be
correctly removed via VM settings window (it is displayed as Unknown
device).
fixesQubesOS/qubes-issues#2789
The button is in 'devices' tab of VM settings; it allows the user to
select which devices should have 'no-strict-reset' enabled and tells
the user not to change this setting if there are no errors.
fixesQubesOS/qubes-issues#3205