TableView: unnamed visual cells are named by their column, not 'blank'

ReadDisplayName only checked for an unnamed visual (a ProgressBar, say) while a
cell was being edited, because the display element exists only then. Check the
cell's own content otherwise, so VerifyUnnamedVisualCellIsNotNamedBlank passes;
cells showing only empty text still read 'blank'.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b54b3a5d-2e82-43fa-9664-760e896cc4a3

controls/dev/TableView/TableViewCellAutomationPeer.cpp

@@ -418,7 +418,8 @@ winrt::hstring TableViewCellAutomationPeer::ReadDisplayName(winrt::TableView con
     if (valueText.empty())
     {
         // An unnamed visual (a ProgressBar, say) is not blank; name it by its column instead.
-        if (display && !ShowsNoCellContent(display, 8))
+        auto const content = display ? display : GetCellContentElement(Owner().try_as<winrt::FrameworkElement>());
+        if (content && !ShowsNoCellContent(content, 8))
         {
             return GetColumnHeaderText(table);
         }