Knowing how annoying re-logins in corporate environments can be, I think
we can open the browser and copy the code to the clipboard (what the user
asks for) without forcing it upon users (which I assume was the reason
it was removed in 8f0e9251b9).
This change adds optional browser opening and code copying during
device-code login after an additional confirmation (usually Enter).
It should work for all providers, with an optional opt-out controlled
by the provider author, not user settings.
Fixes#9282.
