Restore propagation of EVT_SEARCHCTRL_CANCEL_BTN events to the parent.

This was broken by r72581, add event.Skip() call to the handler for this event
added there.

Also add a handler for this event to the corresponding page of the widgets
sample to be able to test this.

Closes #14799.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72915 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/srchctlg.cpp

@@ -1176,9 +1176,10 @@ void wxSearchCtrl::RecalcBitmaps()
     }
 }
 
-void wxSearchCtrl::OnCancelButton( wxCommandEvent& WXUNUSED(event) )
+void wxSearchCtrl::OnCancelButton( wxCommandEvent& event )
 {
     m_text->Clear();
+    event.Skip();
 }
 
 void wxSearchCtrl::OnSetFocus( wxFocusEvent& /*event*/ )