[Security] Initialize SwitchUserEvent::targetUser on attemptExitUser
[Security] Initialize SwitchUserEvent::targetUser on attemptExitUser

The `SwitchUserEvent` is triggered in case an account is switched. This works okay while switching to the user, but on exit the `SwitchUserEvent` is triggered again with the original User. That User was not initialized by the provider yet.

load user by UserInterface instead of username

symfony/security-http