[ADD] auth_totp_mail: 2FA using code sent by email

Add the possibility to force the two-factor authentication for all users,
using a two-factor authentication by email
when the 2FA using an Authenticator app is not configured for the user.

Two possibilities:
 - Force the 2FA only for employee users using the system parameter `auth_totp.policy=employee_required`
 - Force the 2FA for all users, employees and portals, using the system parameter `auth_totp.policy=all_required`

closes odoo/odoo#83750

Signed-off-by: Denis Ledoux (dle) <dle@odoo.com>