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/TriangleSelector.cpp

@@ -1,12 +1,31 @@
 #include "TriangleSelector.hpp"
+#include "Geometry.hpp"
 #include "Model.hpp"
 #include "AABBTreeIndirect.hpp"
+#include "Point.hpp"
+#include "libslic3r.h"
+#include "Utils.hpp"
+#include "TriangleMesh.hpp"
 
+#include <algorithm>
+#include <array>
+#include <Eigen/Geometry>
+#include <Eigen/Core>
 #include <boost/container/small_vector.hpp>
 #include <boost/log/trivial.hpp>
+#include <cmath>
+#include <cassert>
 #include <cstddef>
+#include <cstring>
+#include <cstdint>
+#include <cstdlib>
 #include <functional>
+#include <memory>
+#include <optional>
 #include <tbb/parallel_for.h>
+#include <utility>
+#include <vector>
+#include <queue>
 
 #ifndef NDEBUG
 //    #define EXPENSIVE_DEBUG_CHECKS