Use conventional verb method names in XmlNode

[elharo]

fixes #11582

[slachiewicz]

@elharo we are close to cut maven 4, what is plan for this change?

[elharo]

Let me see what I can do about this. It's a mess because of a Modello.

[elharo]

ATM I'm stymied by a weird case where org.codehaus.plexus.util.xml.Xpp3Dom depends on XmlNode. That dependency seems to be running the wrong direction. Nothing in plexus should depend on Maven.

[slachiewicz]

@elharo In Maven 4, the relationship between Plexus and Maven XML was inverted by design:

• org.apache.maven.api.xml.XmlNode is the immutable core API in Maven 4.
• plexus-xml 4.x was created specifically as a backward-compatibility bridge for legacy plugins—org.codehaus.plexus.util.xml.Xpp3Dom in plexus-xml 4.x wraps and delegates to XmlNode.

Because plexus-xml is an external dependency (codehaus-plexus/plexus-xml), modifying or removing existing method names on XmlNode breaks compatibility with the released plexus-xml 4.x artifacts.

Given that we are close to cutting the Maven 4 release:

1. We should avoid breaking changes to XmlNode at this stage (or only add getter aliases as default methods rather than renaming existing ones).
2. Otherwise, this would require coordinating a release of plexus-xml before we can integrate changes here.

What do you think about either adding default getter methods alongside the current methods or deferring this cleanup post-4.0?