[Register Service] ServiceRole names are inconsistent with other services

The Service roles are defined as follows:

public final class ServiceRole {
    public static final String VIEWER = "users.datalake.viewers";
    public static final String EDITOR = "users.datalake.editors";
    public static final String ADMIN = "users.datalake.admins";
    public static final String OPS = "users.datalake.ops";
    public static final String CRON = "cron.job";
}

• They are inconsistent with the other service role names. For example, storage has "service.storage.admin" etc
• Service roles in Register service are defined as 'User' roles.
• CRON role should be prefixed with the service name for better identification

Proposed change:

public final class ServiceRole {
    public static final String VIEWER = "service.register.viewer";
    public static final String EDITOR = "service.register.editor";
    public static final String ADMIN = "service.register.admin";
    public static final String OPS = "service.register.ops";
    public static final String CRON = "service.register.cron";
}