Ease reuse of provider classpath outside Maven

### New feature, improvement proposal

For IDE integrations it is often necessary to retrieve the provider classpath as determined by m-surefire-p. Currently this requires reflection to access private methods and package private classes.

The issue mentions IDE integrations and the provider classpath determined by m-surefire-p, but names no files, tests, or entry points. Start by locating the provider classpath calculation and its current private or package-private access; done means IDE integrations can reuse that classpath without reflection.

Written by the indexing model from the issue text.