Refactor email verification to a Vue component

What does this MR do and why?

This MR turns the required email verification page into a Vue component, as a first step to implement the allow user to update their email address when requiring email verification for the first time issue.

Issue: https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/413

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the feature flag in Rails console

   Feature.enable(:require_email_verification)

2. Sign out from dev environment
3. Sign in 3 times with a wrong password
4. Sign in with your correct password
5. Copy the code from the verification email (check http://localhost:3000/rails/letter_opener/)
6. Paste the code in the verification form

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.