[safety] Refactor ComponentsInstantiationWizardPageBackend class

TODO (VA) Many of the classes in this package look like this one, no possibility of factorizing?
TODO (AB) I agree. createControl is almost the same and so is applyVisualSelection

(from redmine: issue id 3172, created on 2017-11-17, closed on 2020-06-10)

• Relations:
  • parent #3170 (closed)