Rest of the path chaining has been replaced with the new algorithm.

PolylineCollection.cpp/hpp was removed, use Polylines instead.
Various first_point() / last_point() now return references, not copies.

src/libslic3r/Fill/Fill3DHoneycomb.cpp

@@ -176,7 +176,7 @@ void Fill3DHoneycomb::_fill_surface_single(
             }
         }
         bool first = true;
-        for (Polyline &polyline : chain_infill_polylines(std::move(polylines))) {
+        for (Polyline &polyline : chain_polylines(std::move(polylines))) {
             if (! first) {
                 // Try to connect the lines.
                 Points &pts_end = polylines_out.back().points;