Revert "Address the poor performance of the existing unique-name generation (#17944)"

This reverts commit 83202d8ad6.

# Conflicts:
#	src/Base/Tools.cpp
#	src/Base/Tools.h

src/App/DocumentObject.h

@@ -513,14 +513,7 @@ public:
     {
         return false;
     }
-    /// Handle Label changes, including forcing unique label values,
-    /// signalling OnBeforeLabelChange, and arranging to update linked references,
-    /// on the assumption that after returning the label will indeed be changed to
-    /// the (altered) value of newLabel.
-    /// Returns a vector of referenging (linking) properties as produced by
-    /// PropertyLinkBase::updateLabelReferences which is needed for undo/redo purposes.
-    std::vector<std::pair<Property*, std::unique_ptr<Property>>>
-    onProposedLabelChange(std::string& newLabel);
+
     /*** Called to let object itself control relabeling
      *
      * @param newLabel: input as the new label, which can be modified by object itself
@@ -772,10 +765,10 @@ protected:  // attributes
     /// Old label; used for renaming expressions
     std::string oldLabel;
 
-private:
     // pointer to the document name string (for performance)
     const std::string* pcNameInDocument {nullptr};
 
+private:
     // accessed by App::Document to record and restore the correct view provider type
     std::string _pcViewProviderName;