fix(client): Ensure the web-channel flows match expected behavior.

* Only the signin flow should close the window, all others should redirect.
* Add more functional tests for this case.

issue #1816
issue #1818
issue #1936
issue #1940
fix(client): WebChannel/Hello screen and event fixes.

* Ensure Hello users see the "ready" screen when an account is verified.
* Ensure the "oauth_complete" message is sent to the browser for sign up and password reset, even if the original tab is closed.
* Add more functional tests for the replace original tab and verify in a separate tab cases.

fixes #1818
issue #1936
issue #1938
issue #1940