Fix setting ProjectMetadataElement.Name

[dfederm]

Fixes #10671

Currently the ProjectMetadataElement.Name setter updates the XmlNode for ProjectMetadataElement, but when the metadata is expressed as an attribute it does not update the attribute on the parent node.

This change does the bookeeping for the parent node.

One interesting tidbit is how even when expressed as an attribute, ProjectMetadataElement still uses an (unparented) XmlElementWithLocation to represent it.

[JanKrivanek]

Thank you!