[MNG-7479] Export the package org.apache.maven.eventspy

**[Christoph Läubrich](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=laeubi)** opened **[MNG-7479](https://issues.apache.org/jira/browse/MNG-7479?redirect=false)** and commented

I'm currently try to fetch a specific EventSpy to inject an event there (maven-profiler).

Sadly in my maven plugin when I try to get it injected:

 `@Requirement`(role = EventSpy.class, hint = "profiler", optional = true)
 EventSpy eventSpy;

This results in ClassNotFoundException: org.apache.maven.eventspy.EventSpy

I noticed that the maven-core do not export the 'org.apache.maven.eventspy' package and that is the cause of this, I'd like to suggest to export the package as there seem no other standard way to interact/access event spys otherwise.

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**Affects:** 3.8.5

**Issue Links:**
- [MSHARED-650](https://issues.apache.org/jira/browse/MSHARED-650) Fire ExecutionEvent from DefaultMavenReportExecutor

**Remote Links:**
- [GitHub Pull Request #740
](https://github.com/apache/maven/pull/740)