ENH: wireframe: refine the rendering logic under paint

1. remove wireframe in 3d view, only keep in paint;
2. pass barycentric_coordinates from outside
3. add shortcut hints

Change-Id: I911e5cdf3475926d9527dc0839fdce072ed54746
(cherry picked from commit 6e16d0ccfb71741e55daabd757be9f9e7613e695)

src/slic3r/GUI/Plater.cpp

@@ -1632,7 +1632,7 @@ struct Plater::priv
 
     bool                        show_render_statistic_dialog{ false };
     bool                        show_wireframe{ false };
-    bool                        wireframe_enabled{ false };
+    bool                        wireframe_enabled{ true };
 
     static const std::regex pattern_bundle;
     static const std::regex pattern_3mf;