Fix user_pass_reset_url() deprecation compatibility in AuthCodeFunctionalTest

Problem/Motivation

AuthCodeFunctionalTest fails on Drupal 11.4+ because user_pass_reset_url() is deprecated but there is no working compatibility shim in place.

Proposed resolution

Use DeprecationHelper::backwardsCompatibleCall() to call the new OneTimeAuthentication service on 11.4+ and fall back to user_pass_reset_url() on older versions:

use Drupal\Component\Utility\DeprecationHelper;
use Drupal\user\OneTimeAuthentication;

$reset_url = DeprecationHelper::backwardsCompatibleCall(
  \Drupal::VERSION,
  '11.4.0',
  fn () => \Drupal::service(OneTimeAuthentication::class)->generateOneTimeLoginUrl($new_user)->toString(),
  fn () => user_pass_reset_url($new_user),
);

Remaining tasks

• Apply the fix in tests/src/Functional/AuthCodeFunctionalTest.php