Move XML parsing into its own Standard.XML module

[JaroslavTulach]

XML specification and XML support in JDK is quite bloated. Moreover it is even packaged in its own Java module - it is not part of java.base.

We should move the XML support out of Standard.Base library in order to not force people to include JDK's java.xml module.

Originally posted by @JaroslavTulach in #10296 (comment)

When at it, please: refactor the polyglot java import of XML classes. Rather than importing org.w3c.dom interfaces, import "only" own wrapper XML_Utils with static methods.