Make core/ includes absolute, remove subfolders from include path

This allows more consistency in the manner we include core headers,
where previously there would be a mix of absolute, relative and
include path-dependent includes.

modules/gdnative/pluginscript/pluginscript_loader.cpp

@@ -29,7 +29,7 @@
 /*************************************************************************/
 
 // Godot imports
-#include "os/file_access.h"
+#include "core/os/file_access.h"
 // Pythonscript imports
 #include "pluginscript_language.h"
 #include "pluginscript_loader.h"

modules/gdnative/pluginscript/pluginscript_loader.h

@@ -32,9 +32,9 @@
 #define PYTHONSCRIPT_PY_LOADER_H
 
 // Godot imports
+#include "core/io/resource_loader.h"
+#include "core/io/resource_saver.h"
 #include "core/script_language.h"
-#include "io/resource_loader.h"
-#include "io/resource_saver.h"
 
 class PluginScriptLanguage;
 

modules/gdnative/pluginscript/register_types.cpp

@@ -30,11 +30,11 @@
 
 #include "register_types.h"
 
+#include "core/io/resource_loader.h"
+#include "core/io/resource_saver.h"
+#include "core/os/dir_access.h"
+#include "core/os/os.h"
 #include "core/project_settings.h"
-#include "io/resource_loader.h"
-#include "io/resource_saver.h"
-#include "os/dir_access.h"
-#include "os/os.h"
 #include "scene/main/scene_tree.h"
 
 #include "pluginscript_language.h"