feat(test): Add more functional tests!

* Add functional tests to check users who verify by replacing the original tab, and users who verify by closing the original tab and open a new tab. This is for both OAuth and Sync, for sign up and reset password.
* Add a functional test for signing into sync with an unverified account

fixes #1935
issue #1936
issue #1938
issue #1940
issue #1816
Merge pull request #1944 from mozilla/issues-1935-1940-more-functional-tests

feat(test): Add more functional tests!