[Login] Improve login flow for accounts with suspicious emails

[hichamboushaba]

Use Magic Login for accounts that use suspicious emails (unverified) instead of asking them to sign in using their usernames:
pe5sF9-3H5-p2

Tasks

Preview Give feedback

1. Login: show Magic Link request screen when receiving the email_login_not_allowed error. #13331
   feature: login type: enhancement +2
   
2. Login: update the Magic Link request screen to show a button to use username/password login for suspicious emails. #13341
   feature: login type: enhancement +2
   
3. Jetpack Setup: show Magic Link request screen when receiving the email_login_not_allowed error.
4. Jetpack Setup: update the Magic Link request screen to show a button to use username/password login for suspicious emails

[dangermattic]

Thanks for reporting! 👍