Backward compatibility fix for UserAuthenticationInterface

Problem/Motivation

An error message displayed when the mail_login module is used together with the TFA module.
TypeError:
Drupal\mail_login\AuthDecorator::__construct(): Argument #1
($user_auth) must be of type Drupal\user\UserAuthenticationInterface,
Drupal\tfa\TfaUserAuth given

Steps to reproduce

Use latest version of mail_login module (4.0.3)
Use latest version of TFA (2.0.0-alpha4)
Enable both modules using Drupal core 10.3.10.

Proposed resolution

The maintainer of TFA suggested to address the issue in mail_login, therefore I created a fix.
After applying the patch no error is triggered any more.

Remaining tasks

These checks won't be necessary any more when the old UserAuthInterface will be retired in Drupal 12, until that we need some changes to make them work together.
Old interface: https://git.drupalcode.org/project/drupal/-/blob/10.3.x/core/modules/use...
New interface: https://git.drupalcode.org/project/drupal/-/blob/10.3.x/core/modules/use...