[JENKINS-47768] - Avoid having "authenticated" twice in the group membership...

[JENKINS-47768] - Avoid having "authenticated" twice in the group membership of a user (LastGrantedAuthorities) (#3123)

* Avoid having "authenticated" twice in the group membership of a user
- this occur when the SecurityRealm potentially already grants that role (like in github-oauth-plugin)

* - changed as requested by Oleg
- the list has a maximum of roles.length and in reality it's either roles.length or (roles.length-1), so the maximum is ok

* - fix problem of missing the "authenticated" authority

* - convert the Groovy script to a Java version
- the Groovy test was not run by default (IIUC Groovy scripts are not compiled if placed in java src folder)