[MNG-8559] Rewrite DefaultPluginManager with Maven 4 API

**[Guillaume Nodet](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=gnt)** opened **[MNG-8559](https://issues.apache.org/jira/browse/MNG-8559?redirect=false)** and commented

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**Issue Links:**
- [MNG-6135](https://issues.apache.org/jira/browse/MNG-6135) Maven plugins and core extensions are not dependencies, they should be resolved the same way as projects.
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- [MNG-8451](https://issues.apache.org/jira/browse/MNG-8451) Core should inject "managed" dependency management during plugin resolution
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- [MNG-2893](https://issues.apache.org/jira/browse/MNG-2893) Update the DefaultPluginManager to not use a project depMan for controlling its transitive dependencies
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Start by locating DefaultPluginManager and reading the linked issues MNG-6135, MNG-8451, and MNG-2893 to understand the existing resolution behavior and Maven 4 API expectations. Done means the manager has been rewritten to use the Maven 4 API while addressing the linked plugin and core-extension dependency concerns.

Written by the indexing model from the issue text.