[MNG-7591] Enhance MavenWorkspaceReader to find workspace projects

**[Christoph Läubrich](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=laeubi)** opened **[MNG-7591](https://issues.apache.org/jira/browse/MNG-7591?redirect=false)** and commented

The org.apache.maven.repository.internal.MavenWorkspaceReader currently allows for finding a model for a given artifact.

But recently I noticed at m2eclipse (IDE extension) that when loading a maven project maven also loads all the parent projects, of course we have them in the IDE as well, so such action can lead to multiple times loading the same maven project.

I therefore like to suggest to enhance MavenWorkspaceReader with a method:

MavenProject findProject( Artifact artifact );

or just

MavenProject findProject( File pomFile );

to allow for example DefaultProjectBuilder to take this into account when loading parents.

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**Issue Links:**
- [MNG-7496](https://issues.apache.org/jira/browse/MNG-7496) DefaultArtifactDescriptorReader.loadPom() should query the MavenWorkspaceReader first