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/NSVGUtils.cpp

@@ -1,11 +1,24 @@
 #include "NSVGUtils.hpp"
 #include <array>
+#include <cassert>
 #include <charconv> // to_chars
 
 #include <boost/nowide/iostream.hpp>
 #include <boost/nowide/fstream.hpp>
+#include <nanosvg/nanosvg.h>
+#include <cstddef>
+#include <string>
+#include <memory>
+#include <sstream>
+#include <cstring>
+#include <cmath>
 #include "ClipperUtils.hpp"
 #include "Emboss.hpp" // heal for shape
+#include "Polygon.hpp"
+#include "Polyline.hpp"
+#include "EmbossShape.hpp"
+#include "Point.hpp"
+#include "libslic3r.h"
 
 namespace {    
 using namespace Slic3r; // Polygon