[MNG-8753] delete DependencyManagementImporter

**[Elliotte Rusty Harold](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=elharo)** opened **[MNG-8753](https://issues.apache.org/jira/browse/MNG-8753?redirect=false)** and commented

Another case of excess abstraction where several public classes and interfaces look able to be reduced to a single private static method. The public API can be reintroduced later if there's ever a need for it, but more likely YAGNI. It's worth checking this for everything in org.apache.maven.api.services.model

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