[CLI FEATURE] Command for deleting an admin user by the given username

[crydotsnake]

Describe the proposed solution

In the issue #14172 I introduced the suggestion that it would be good to have a CLI command for creating an admin user. Here in this issue it is about the reverse case ;) namely the deletion of an admin user based on the given username.

Procedure of the command:

• User is asked for the username
• If the username does not exist, a warning is displayed in the console.
• If the username is correct, the username is searched for in the UserRepositoryInterface and deleted from the database and sylius admin panel.

Describe alternatives you've considered
None

Additional context
None

[crydotsnake]

As an alternative to the email address the user could also be deleted via the username of course.