Fixed setting colours of wxSlider and wxRadioBox in wxMSW.

Sibling windows (like labels and radio buttons) need to be explicitly
refreshed when foreground or background colour is changed. This is implemented
by invoking newly implemented method wxSubwindows::Refresh every time the
colour of the control is changed.

Note: Setting foreground colour of wxRadioBox still doesn't work correctly
when themes are enabled.

Closes #17142.

include/wx/msw/slider.h

@@ -91,6 +91,8 @@ public:
     virtual bool Show(bool show = true);
     virtual bool Enable(bool show = true);
     virtual bool SetFont(const wxFont& font);
+    virtual bool SetForegroundColour(const wxColour& colour);
+    virtual bool SetBackgroundColour(const wxColour& colour);
 
     virtual WXDWORD MSWGetStyle(long flags, WXDWORD *exstyle = NULL) const;