bug #18693 add @Event annotation for AuthenticationEvents (Haehnchen)

This PR was merged into the 3.1-dev branch.

Discussion
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add @Event annotation for AuthenticationEvents

| Q             | A
| ------------- | ---
| Branch       | 2.3
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #18684
| License       | MIT

split of #18684 for targeting 2.3 branch

Commits
-------

e2c1270 add @Event annotation for AuthenticationEvents

src/Symfony/Component/Security/Core/AuthenticationEvents.php

@@ -20,6 +20,8 @@ final class AuthenticationEvents
      * The event listener method receives a
      * Symfony\Component\Security\Core\Event\AuthenticationEvent instance.
      *
+     * @Event
+     *
      * @var string
      */
     const AUTHENTICATION_SUCCESS = 'security.authentication.success';
@@ -32,6 +34,8 @@ final class AuthenticationEvents
      * Symfony\Component\Security\Core\Event\AuthenticationFailureEvent
      * instance.
      *
+     * @Event
+     *
      * @var string
      */
     const AUTHENTICATION_FAILURE = 'security.authentication.failure';