Address Review of the Reworked Unit Tests

Recompute the v4 recipe comparison once instead of per feature (148 s to 6 s) and compare bounding boxes as well as volumes; drop the incidental NaN loop from the unrepairable Voronoi case; prove the renamed preset is the one selected instead of checking a dirty flag that selecting clears; tell sparse from empty infill in the solid-shell test; plus smaller cleanups.

tests/fff_print/test_trianglemesh.cpp

@@ -2,7 +2,7 @@
 
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers_floating_point.hpp>
-#include "catch2/matchers/catch_matchers.hpp"
+#include <catch2/matchers/catch_matchers.hpp>
 #include "libslic3r/TriangleMesh.hpp"
 #include "libslic3r/TriangleMeshSlicer.hpp"
 #include "libslic3r/Point.hpp"