Reimplement adding items to radio groups in wxMenu (wxOSX)

Rewrote wxOSX radio groups-related code reusing the code which works on
wxMSW and which seems to provide more rich functionality (supports adding
radio as well as no-radio items) and to have known bugs fixed.
The ranges of all radio groups are stored in wxMenu itself instead of
storing the information about the radio group an item belongs to in
the item itself - see 89511b4268.

Closes #14213.
Closes #17568.

include/wx/osx/menuitem.h

@@ -53,41 +53,10 @@ public:
     void UpdateItemText() ;
     void UpdateItemStatus() ;
 
-    // mark item as belonging to the given radio group
-    void SetAsRadioGroupStart(bool start = true);
-    void SetRadioGroupStart(int start);
-    void SetRadioGroupEnd(int end);
-
-    // return true if this is the starting item of a radio group
-    bool IsRadioGroupStart() const;
-
-    // get the start of the radio group this item belongs to: should not be
-    // called for the starting radio group item itself because it doesn't have
-    // this information
-    int GetRadioGroupStart() const;
-
-    // get the end of the radio group this item belongs to: should be only
-    // called for the starting radio group item, i.e. if IsRadioGroupStart() is
-    // true
-    int GetRadioGroupEnd() const;
-
     wxMenuItemImpl* GetPeer() { return m_peer; }
 private:
     void UncheckRadio() ;
 
-    // the positions of the first and last items of the radio group this item
-    // belongs to or -1: start is the radio group start and is valid for all
-    // but first radio group items (m_isRadioGroupStart == FALSE), end is valid
-    // only for the first one
-    union
-    {
-        int start;
-        int end;
-    } m_radioGroup;
-
-    // does this item start a radio group?
-    bool m_isRadioGroupStart;
-
     wxBitmap  m_bitmap; // Bitmap for menuitem, if any
 
     wxMenuItemImpl* m_peer;