Test XmlSerialization of class with XmlSchemaProvider with IsAny.
Covers #11916.
Fixed XmlSerializer to handle attribute XmlSchemePrivider.IsAny.
XmlSerializer no longer outputs a root element with class name when the class has the attribute XmlSchemeProvider and IsAny is true.
Fixes #11916
Merge pull request #1212 from esdrubal/isany

Fixed XmlSerializer to handle attribute XmlSchemePrivider.IsAny.