Add Missing Includes Across src/libslic3r

Every libslic3r source and header now directly includes the headers declaring what it uses, rather than relying on the precompiled header or transitive includes. Generated with clang-tidy misc-include-cleaner, with libslic3r headers spelled libslic3r/... so they resolve outside the library's private include paths. MultiMaterialSegmentation.hpp, Support/SupportParameters.hpp and Format/STEP.hpp are made self-contained by hand.

src/libslic3r/CAD/SketchConstraints.cpp

@@ -1,6 +1,11 @@
 #include "libslic3r/CAD/SketchConstraints.hpp"
+#include "libslic3r/Point.hpp"
+#include <Eigen/Core>
 #include <Eigen/Dense>
+#include <algorithm>
 #include <cmath>
+#include <cstddef>
+#include <vector>
 
 namespace Slic3r {