R1:41d9453ece06

When a user changes to a verified primary address, mark their account as verified

Summary:
Ref T12635. See that task for discussion.

You can currently end up with a verified primary address but no "verified" flag on your account through an unusual sequence of address mutations.

Test Plan:
- Registered without verifying, using address "A".
- Added a second email address, address "B".
- Verified B (most easily with `bin/auth verify`).
- Changed my primary email to B.
- Before patch: account not…