Add Missing Includes Across src/slic3r/GUI (#16048)

* Add Missing Includes Across src/slic3r/GUI

Every GUI 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, plus one hand edit making CalibrationPanel.hpp self-contained.

* Drop the OS-Specific Includes Added Outside Their Platform Guards

GLib, GTK, D-Bus and POSIX headers are only used inside platform #if blocks, which already include them. Added unconditionally at the top of the file they broke the Windows build.

* Add the clang-tidy Configuration That Generated These Includes

Only misc-include-cleaner's missing-include check, with the headers it must never suggest: per-platform, internal and OS-specific ones that would break other platforms or are not meant to be included directly.

* Match Windows Paths in the clang-tidy Ignore List

Header paths use backslashes on Windows, so every / in a pattern is now [/\\]. The Windows SDK headers are ignored alongside the other OS-specific ones, and the list is one pattern per line. Suggested by @raistlin7447 from a Windows clang-cl run.

src/slic3r/GUI/DownloaderFileGet.cpp

@@ -1,5 +1,16 @@
 #include "DownloaderFileGet.hpp"
 
+#include <cstddef>
+#include <string>
+#include <boost/algorithm/string/predicate.hpp>
+#include <atomic>
+#include <regex>
+#include <cassert>
+#include <boost/filesystem/exception.hpp>
+#include <cstdio>
+#include <boost/filesystem/operations.hpp>
+#include <exception>
+#include <stdexcept>
 #include <thread>
 #include <curl/curl.h>
 #include <boost/nowide/fstream.hpp>
@@ -8,6 +19,8 @@
 #include <boost/log/trivial.hpp>
 #include <boost/algorithm/string.hpp>
 #include <iostream>
+#include <wx/event.h>
+#include <utility>
 
 #include "format.hpp"
 #include "GUI.hpp"