Repeated email verification refresh calls when the backend is not running

[porcellus]

We are calling user/email/verify GET 5 times when:

• the user is already logged in
• hasn't completed email verification
• loads the email verification page

To resolve, we want to implement 2 improvements:

1. Skip adding the email verification validator from web-js if we are already adding it in auth-react
2. Add a global, in-memory cooldown for each refresh function. In the shouldRefresh calls we should check this cooldown by default and limit refresh calls to no more than 1 per second.