[Windows App] Allow specifying which camera to use for setup-via-QR code

Thanks ag_mike_d ! Appreciate all your help. And yes I've been able to login via another method in the meantime. The computer where I was doing this login is a PC I keep around for test purposes and its fairly often reset to a clean boot. All that to say, having faster ways to sign in such as with the QR code will be very helpful to me as a 1Password user on this PC and I'm crossing my fingers that this feature will show up in the future :)