Move non-output to new CppUtils namespace

We prefer to have the Outputs directory contain just one file or
namespace per output module, so we'll move all C++-related stuff to a
new CppUtils namespace instead.

Il2CppInspector.GUI/MainWindow.xaml.cs

@@ -28,7 +28,7 @@ using Il2CppInspector.Outputs;
 using Il2CppInspector.Reflection;
 using Ookii.Dialogs.Wpf;
 using Path = System.IO.Path;
-using Il2CppInspector.Outputs.UnityHeaders;
+using Il2CppInspector.CppUtils.UnityHeaders;
 
 namespace Il2CppInspectorGUI
 {