Collapse primary_user modules

Reduces duplicate code.
See Issue #3184
lockdown
fix lint tests
revert bcrypt upgrade
single module
Cleanup and simplification.

* Rename upgrade_verify_primary_user back to verify_primary_user
* Simplify the state machine w.r.t. doUpgradePrimaryUser and upgrade_to_primary
* Simplify verify_primary_user's core logic.
* Rename the #verifyWithPrimary button to .verifyWithPrimary

fixes #3357
Code clarification.
Thanks @ozten!
Merge pull request #3458 from mozilla/issue-3184-consolidate-verify-with-primary

Issue 3184 consolidate verify with primary