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_

从提交 e895fc7c1012796442cb7a4a3b9b3a0ec3845b0e 开始，检查从 CDK 移至 schematics 包的独立辅助函数。确定 private 部分如何暴露它们，然后验证这些辅助函数是否被视为 public API；如果该包有相关 coverage，则更新或添加它。

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