KIM Migrator - RBAC migration code updates

[koala7659]

During migration of CRBs we have taken all subjects from CRBs labeled with reconciler.kyma-project.io/managed-by=reconciler,app=kyma and turned them into CRB with subject of User type type with cluster-admin access.

• We did not check if they were previously cluster-admins or not.
• We did not if they were previously kind of User type (edited)

Code changes:

• Add filtering for to migrate only Cluster Role Bindings of cluster-admins access level.
• Add filtering for to migrate only Cluster Role Bindings with subject of User type.
• Enhance the migration logic to add an deprecation-label to each CRB with that will be migrated: kyma-project.io/deprecation: this ClusterRoleBinding is deprecated and will be removed in next days!

Relates issue:
#556