R1:a017a8e02b51

Make two-factor auth actually work

Summary:
Ref T4398. Allows auth factors to render and validate when prompted to take a hi-sec action.

This has a whole lot of rough edges still (see D8875) but does fundamentally work correctly.

Test Plan:
- Added two different TOTP factors to my account for EXTRA SECURITY.
- Took hisec actions with no auth factors, and with attached auth factors.
- Hit all the error/failure states of the hisec entry process.
- Verified hisec failures appear in activity logs.