Rework security to use Vaadin 22's AccessAnnotationChecker

[mvysny]

In Vaadin 21+ there's the AccessAnnotationChecker class and the ViewAccessChecker class which helps with LoginView and uses a simple role-based security based on javax.annotation.security.RolesAllowed annotations.

VoK should drop its own annotations and use the abovementioned classes, to reuse a lot of tested code.

Namely:

• eu.vaadinonkotlin.security.AllowAll is replaced by Vaadin 21+'s com.vaadin.flow.server.auth.AnonymousAllowed.

[mvysny]

The AccessAnnotationChecker is not present in Vaadin 14 LTS, therefore this ticket is blocked by #72 .

However, what we can do is to drop the eu.vaadinonkotlin.security.* annotations in favor of javax.annotation.security.* annotations. Blocked by #73

[mvysny]

Note to also update README.md and security.md documentation.