Stop Format/STEP.hpp Defining a Global fs Alias (#16102)

Every file that included STEP.hpp, directly or not, got namespace fs = boost::filesystem at global scope, and 29 sources and three headers relied on it without saying so. Headers now spell out boost::filesystem, and each source that uses fs declares the alias itself.

src/slic3r/GUI/AuxiliaryDataViewModel.cpp

@@ -21,6 +21,8 @@
 #include <wx/variant.h>
 #include <wx/types.h>
 
+namespace fs = boost::filesystem;
+
 const static std::array<wxString, 4> s_default_folders = {
     _L("Model Pictures"),
     _L("Bill of Materials"),