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/SketchSolver.cpp

@@ -1,5 +1,7 @@
 #include "libslic3r/CAD/SketchSolver.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
 
+#include <math.h>
 #include <slvs.h>
 
 #include <cmath>
@@ -7,6 +9,8 @@
 #include <functional>
 #include <map>
 #include <unordered_map>
+#include <vector>
+#include <utility>
 
 namespace Slic3r {