WIP: Refactored bridging flow from normal flow, new config value

'thick_bridges' to switch between the Slic3r vs. S3D/Cura/Ideamaker
way of printing 1st object layer over supports.
Simplified the PresetHints.

src/libslic3r/Layer.hpp

@@ -59,7 +59,9 @@ public:
     // (this collection contains only ExtrusionEntityCollection objects)
     ExtrusionEntityCollection   fills;
     
-    Flow    flow(FlowRole role, bool bridge = false, double width = -1) const;
+    Flow    flow(FlowRole role) const;
+    Flow    bridging_flow(FlowRole role) const;
+
     void    slices_to_fill_surfaces_clipped();
     void    prepare_fill_surfaces();
     void    make_perimeters(const SurfaceCollection &slices, SurfaceCollection* fill_surfaces);