Promote standalone component helpers to public API

### Command

add

### Description

With https://github.com/angular/angular-cli/commit/e895fc7c1012796442cb7a4a3b9b3a0ec3845b0e a few standalone helpers were moved from the CDK to the schematics package. I am wondering why they were moved to a "private" section and aren't considered public API. Was this just because standalone components were still in developer preview at that time? Now that angular 15 is going to make standalone components stable could the helpers be moved outside the private section and be treated as public API?

### Describe the solution you'd like

With standalone components becoming stable these helpers should become public API as well.

### Describe alternatives you've considered

_No response_

Commencez par le commit e895fc7c1012796442cb7a4a3b9b3a0ec3845b0e et examinez les helpers autonomes déplacés du CDK vers le package schematics. Déterminez comment la section privée les expose, puis vérifiez que les helpers sont traités comme une API publique et mettez à jour ou ajoutez la couverture pertinente si le package en dispose.

Rédigé par le modèle d'indexation à partir du texte de l'issue.