Remove Duplicate Includes and the Dead GCodeSender Sources (#16249)

46 files include the same header twice at file scope, outside any #if,
66 times in all:
Model.cpp included Model.hpp twice, Utils.hpp <algorithm> and
<string_view> twice, seven GUI headers <wx/dataview.h> and
<wx/artprov.h> twice. The second include of each is removed.

GCodeSender.cpp and GCodeSender.hpp have been commented out of
libslic3r/CMakeLists.txt since 2022 and their only two includes are
commented out as well. Both files go, with the commented lines, and
the CMake entry for SLA/SupportTreeIGL.cpp, a file that no longer
exists.

src/slic3r/GUI/Tab.cpp

@@ -1,4 +1,3 @@
-// #include "libslic3r/GCodeSender.hpp"
 //#include "slic3r/Utils/Serial.hpp"
 #include "Tab.hpp"
 #include "PresetHints.hpp"
@@ -102,8 +101,6 @@
 #include "Widgets/MultiNozzleSync.hpp"
 #include "Widgets/SwitchButton.hpp"
 #include "Widgets/TabCtrl.hpp"
-#include "Widgets/ComboBox.hpp"
-#include "Search.hpp"
 #include "BedShapeDialog.hpp"
 #include "libslic3r/GCode/Thumbnails.hpp"
 #include "WipeTowerDialog.hpp"