Fix U4-5301: Update node name when updating XML cache

When using the new XML schema, the content type alias is the node name itself. When updating the XML cache this is not accounted for, resulting in a Republish entire site being required.
This fixes the issue by updating the node name as well. Due to the fact that the Name property of XmlNode is read only this requires creating a new node instead of just changing the name. This in turn means that we have to replace the node rather than simply updating the existing one.