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/ExtrusionEntity.cpp

@@ -4,10 +4,23 @@
 #include "ClipperUtils.hpp"
 #include "Extruder.hpp"
 #include "Flow.hpp"
+#include <algorithm>
+#include <cassert>
 #include <cmath>
+#include <cstddef>
+#include <functional>
 #include <limits>
 #include <sstream>
+#include "Point.hpp"
+#include "Polyline.hpp"
+#include "Polygon.hpp"
+#include <utility>
+#include <vector>
+#include "Line.hpp"
+#include <string>
+#include <string_view>
 #include "Utils.hpp"
+#include "libslic3r.h"
 
 #define L(s) (s)