EEschema: fix an issue in sheet cross-references of global labels.

Commit 5ca34147 (a cherry pick from master branch) broke these cross-references.
If was fixed later in master branch, but these changes cannot be cherry picked.
So the old code is reused in 2 functions to fix the issue.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/18534

eeschema/schematic.cpp

@@ -453,7 +453,7 @@ std::map<int, wxString> SCHEMATIC::GetVirtualPageToSheetNamesMap() const
 {
     std::map<int, wxString> namesMap;
 
-    for( const SCH_SHEET_PATH& sheet : GetUnorderedSheets() )
+    for( const SCH_SHEET_PATH& sheet : GetSheets() )
     {
         if( sheet.size() == 1 )
             namesMap[sheet.GetVirtualPageNumber()] = _( "<root sheet>" );
@@ -469,7 +469,7 @@ std::map<int, wxString> SCHEMATIC::GetVirtualPageToSheetPagesMap() const
 {
     std::map<int, wxString> pagesMap;
 
-    for( const SCH_SHEET_PATH& sheet : GetUnorderedSheets() )
+    for( const SCH_SHEET_PATH& sheet : GetSheets() )
         pagesMap[sheet.GetVirtualPageNumber()] = sheet.GetPageNumber();
 
     return pagesMap;