Noun method names in XmlNode

### Affected version

4.x

### Bug description

For inobvious reasons methods that follow Java conventions like getChild and getValue have been deprecated and replaced with methods that don't like child() and value(). This is confusing and unnecessary churn. Revert this.

One can argue about the wisdom of Java's well-established naming conventions, but individual projects like Maven should not needlessly deviate from those for personal preference. It's far easier to stick with existing convention than for every project to pave its own way.

And yes, Oracle did a half-assed job when they added records to the language in Java 17 without considering the impact on naming conventions for existing code. That neither conformed to nor changed existing conventions for non-record classes and interfaces.

Start by locating XmlNode and the deprecated getChild and getValue methods in the Maven source, then inspect nearby tests and references to determine the affected API surface. Done means the noun-style method names are restored consistently and the relevant test suite passes without breaking existing callers.

Written by the indexing model from the issue text.