2FA variant of https://phabricator.wikimedia.org/T229264

Note:
We are applying the same fix here as we did in https://phabricator.wikimedia.org/T403480. If automatic login fails due to lack of a 2FA code, the 2FA form should automatically present instead of silently failing.

Test Steps

1. Install app (main 8.0.0 6033), login to 2FA account.
2. Log into same account on web.
3. Log out on web.
4. Do something in the app to trigger background login (relaunch app or visit notifications center, foregrounding the app will also do it on a 30 second cadence).
5. Ensure 2FA code input form appears with its custom message. Enter 2FA code. Ensure screen dismisses and app acts as it did before (logged in, can still load user data).
6. Repeat steps 1 - 6, but this time tap Cancel when 2FA code input form appears. Ensure app logs you out when cancelling