Mark tests that create CodeModelElements to be WpfFact requiring

Right now the CleanableWeakComHandleTable is very affinitized, and until
we can change that we're best leaving these as is.

src/VisualStudio/Core/Test/CodeModel/CodeModelTestHelpers.vb

@@ -145,6 +145,8 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.CodeModel
             Dim result As EnvDTE.CodeElement = Nothing
 
             For Each candidateScope In candidateScopes
+                Roslyn.Test.Utilities.WpfTestCase.RequireWpfFact($"{NameOf(GetCodeElementAtCursor)} creates CodeElements and thus uses the affinited CleanableWeakComHandleTable")
+
                 Try
                     result = state.FileCodeModelObject.CodeElementFromPosition(cursorPosition, candidateScope)
                 Catch