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

Fiddling around with the camera in the default settings app did not change anything. I tried the following
* open camera app, switch camera to backfacing camera, close camera app, try to signin via QR in 1Password app
* open camera app, switch camera to frontfacing camera, close camera app, try to signin via QR in 1Password app
* open camera app, switch camera to backfacing camera, leave camera app open, try to signin via QR in 1Password app
* open camera app, switch camera to frontfacing camera, leave camera app open, try to signin via QR in 1Password app

In most cases, 1Password still only tried to use my frontfacing camera. The only exception was when I left the camera app open with the front facing camera. Then 1Password was just unable to activate any camera and so the QR scanner didn't work at all.

I was somewhat able to force 1Password to open the rear-camera by disabling the frontfacing camera in Device Manager per this article: https://www.lifewire.com/flip-camera-on-surface-pro-5191562

BUT this had its own problems. The image on the rear-facing camera was flipped and when the camera scanned the QR code it failed to complete login (I'm not really sure what's happening here. It just exits back to the login screen once it recognizes the QR code. There's no error message or anything but it's not logging in after scanning the QR code)

I have also tried flipping the QR code around and that didn't seem to fix it either.