Allow to get qualified name via NodeContext

As validators often include node or property names in their validation messages there should be some means to get the qualified name from the org.apache.jackrabbit.spi.Name used in DocViewNode2 and DocViewProperty2.

The easiest way is to add a getter method similar to https://jackrabbit.apache.org/api/2.20/org/apache/jackrabbit/spi/commons/conversion/NameResolver.html#getJCRName-org.apache.jackrabbit.spi.Name- to the NodeContext.