Use of NamespacePrefixMapper has changed in Jarkarta

On the branch jarkarta, some unit tests are failing since I think the use of NamespacePrefixMapper has changed in Jarkarta.

https://mkyong.com/java/jaxb-hello-world-example/#jaxb-xml-marshalling-convert-java-objects-to-xml https://www.jesperdj.com/2018/09/30/jaxb-on-java-9-10-11-and-beyond/