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/PlaceholderParser.cpp

@@ -1,12 +1,52 @@
 #include "PlaceholderParser.hpp"
+#include "Config.hpp"
 #include "Exception.hpp"
 #include "Flow.hpp"
+#include "PrintConfig.hpp"
+#include "Point.hpp"
 #include "Utils.hpp"
+#include "libslic3r_version.h"
+#include <cassert>
+#include <boost/range/iterator_range_core.hpp>
+#include <cmath>
+#include <cstdlib>
+#include <boost/throw_exception.hpp>
+#include <boost/spirit/home/support/info.hpp>
+#include <algorithm>
+#include <cstdio>
+#include <boost/algorithm/string/predicate.hpp>
+#include "libslic3r.h"
+#include <boost/spirit/home/qi/numeric/real_policies.hpp>
+#include <boost/spirit/home/qi/parser.hpp>
+#include <boost/assert/source_location.hpp>
+#include <boost/spirit/home/qi/nonterminal/grammar.hpp>
+#include <boost/spirit/home/qi/nonterminal/rule.hpp>
+#include <boost/spirit/home/support/common_terminals.hpp>
+#include <boost/spirit/home/qi/auxiliary/eps.hpp>
+#include <boost/spirit/home/qi/directive/raw.hpp>
+#include <boost/spirit/home/qi/char/char.hpp>
+#include <boost/spirit/home/qi/directive/lexeme.hpp>
+#include <boost/spirit/home/qi/directive/no_skip.hpp>
+#include <boost/spirit/home/qi/numeric/real.hpp>
+#include <boost/spirit/repository/home/qi/primitive/iter_pos.hpp>
+#include <boost/spirit/repository/home/qi/directive/distinct.hpp>
+#include <boost/spirit/home/qi/copy.hpp>
+#include <boost/spirit/home/qi/action/action.hpp>
+#include <boost/spirit/home/qi/nonterminal/error_handler.hpp>
+#include <boost/spirit/home/qi/nonterminal/debug_handler.hpp>
+#include <boost/spirit/home/qi/string/symbols.hpp>
+#include <boost/spirit/home/qi/parse.hpp>
 #include <cstring>
 #include <ctime>
 #include <iomanip>
+#include <random>
+#include <set>
+#include <memory>
+#include <iterator>
 #include <sstream>
 #include <map>
+#include <vector>
+#include <utility>
 #ifdef _MSC_VER
     #include <stdlib.h>  // provides **_environ
 #else