Move helper to workspace layer

src/Features/Core/Portable/FindUsages/ExternalReferenceItem.cs

@@ -18,12 +18,12 @@ internal abstract class ExternalReferenceItem
 
         public ExternalReferenceItem(
             DefinitionItem definition,
-            string documentName,
+            string projectName,
             object text,
             string displayPath)
         {
             Definition = definition;
-            DocumentName = documentName;
+            ProjectName = projectName;
             Text = text;
             DisplayPath = displayPath;
         }