Netinfo: avoid transitive string_utils.h include

Put the string manipuuation utils in the cpp, and
remove string_utils.h from the includes of netinfo.h.

This spams that header into about 350 files, not all of which
need it. Then go round and tidy up the places (most exporters
and dialogs) where CPP files weren't including string_utils.h
when they used it, as well as some other order-sensitive
include issues that turned up.

pcbnew/python/scripting/pcb_scripting_tool.cpp

@@ -23,18 +23,20 @@
 
 #include "pcb_scripting_tool.h"
 
+#include <Python.h>
+
+#include <wx/string.h>
+
+#include <pybind11/eval.h>
+
 #include <action_plugin.h>
 #include <kiface_ids.h>
 #include <kiway.h>
 #include <macros.h>
 #include <pgm_base.h>
 #include <python_scripting.h>
+#include <string_utils.h>
 #include <tools/pcb_actions.h>
-
-#include <pybind11/eval.h>
-
-#include <Python.h>
-#include <wx/string.h>
 #include <launch_ext.h>
 
 #ifdef KICAD_IPC_API