Reworked the "new" bridging to respect the bridge_flow_ratio

by maintaining extrusion spacing, but modifying the extrusion width
and / or height.

src/libslic3r/Layer.hpp

@@ -60,6 +60,7 @@ public:
     ExtrusionEntityCollection   fills;
     
     Flow    flow(FlowRole role) const;
+    Flow    flow(FlowRole role, double layer_height) const;
     Flow    bridging_flow(FlowRole role) const;
 
     void    slices_to_fill_surfaces_clipped();