As 3.9.3 lost this capability as it goes only for POM (direct dependencies)
while transitive also does tell a lot.

Example output with this PR:
```
[WARNING]
[WARNING] Plugin [INTERNAL, EXTERNAL] validation issues were detected in following plugin(s)
[WARNING]
[WARNING]  * org.jacoco:jacoco-maven-plugin:0.8.10
[WARNING]   Plugin EXTERNAL issue(s):
[WARNING]    * Transitive dependencies contain Maven 2.x artifacts, which will be not supported in Maven 4.x
[WARNING]    * Transitive dependencies mixes multiple Maven versions: [2.0.6, 2.0.2]
[WARNING]    * Transitive dependencies contain plexus-container-default, which is EOL
[WARNING]
[WARNING]  * org.apache.maven.plugins:maven-site-plugin:3.12.1
[WARNING]   Declared at location(s):
[WARNING]    * com.soebes.smpp:smpp:6.0.4-SNAPSHOT (pom.xml) @ line 580
[WARNING]   Plugin EXTERNAL issue(s):
[WARNING]    * Direct dependencies contain Maven 2.x compatibility layer, which will be not supported in Maven 4.x
[WARNING]    * Transitive dependencies of Maven artifacts are not in `provided` scope. If the plugin already declares them in `provided` scope, update the maven-plugin-plugin to latest version. Artifacts found with wrong scope: [org.apache.maven:maven-plugin-api:3.2.5, org.apache.maven:maven-model:3.2.5, org.apache.maven:maven-core:3.2.5, org.apache.maven:maven-settings:3.2.5, org.apache.maven:maven-model-builder:3.2.5, org.apache.maven:maven-repository-metadata:3.2.5, org.apache.maven:maven-aether-provider:3.2.5, org.apache.maven:maven-settings-builder:3.2.5, org.apache.maven:maven-artifact:3.2.5]
[WARNING]    * Transitive dependencies contain plexus-container-default, which is EOL
[WARNING]   Mojo EXTERNAL issue(s):
[WARNING]    * Mojo site:attach-descriptor (org.apache.maven.plugins.site.descriptor.SiteDescriptorAttachMojo)
[WARNING]      - Parameter 'localRepository' uses deprecated parameter expression '${localRepository}': ArtifactRepository type is deprecated and its use in Mojos should be avoided.
[WARNING]
[WARNING]
[WARNING] Fix reported issues by adjusting plugin configuration or by upgrading above listed plugins. If no upgrade available, please notify plugin maintainers about reported issues.
[WARNING] For more or less details, use 'maven.plugin.validation' property with one of the values (case insensitive): [NONE, INLINE, SUMMARY, BRIEF, VERBOSE]
[WARNING]
```

---

https://issues.apache.org/jira/browse/MNG-7826

This is a quickndirty POC that shows it works, but the real
thing would be to generate this from something like extension.xml
is.