Extract ScriptInstance to simplify includes

This allows to include script_instance.h directly in the
generated gdvirtual.gen.inc, and remove excessive includes
from the codebase.

This should also allow Resource to use GDVIRTUAL macros,
which wasn't possible previously due to a circular dependency.

servers/audio/audio_effect.h

@@ -34,7 +34,6 @@
 #include "core/io/resource.h"
 #include "core/math/audio_frame.h"
 #include "core/object/gdvirtual.gen.inc"
-#include "core/object/script_language.h"
 #include "core/variant/native_ptr.h"
 
 class AudioEffectInstance : public RefCounted {

servers/audio/audio_stream.h

@@ -37,7 +37,6 @@
 #include "servers/audio_server.h"
 
 #include "core/object/gdvirtual.gen.inc"
-#include "core/object/script_language.h"
 #include "core/variant/native_ptr.h"
 
 class AudioStream;

servers/extensions/physics_server_2d_extension.h

@@ -33,7 +33,6 @@
 
 #include "core/extension/ext_wrappers.gen.inc"
 #include "core/object/gdvirtual.gen.inc"
-#include "core/object/script_language.h"
 #include "core/variant/native_ptr.h"
 #include "core/variant/type_info.h"
 #include "core/variant/typed_array.h"

servers/physics_server_3d.h

@@ -34,7 +34,6 @@
 #include "core/io/resource.h"
 #include "core/object/class_db.h"
 #include "core/object/gdvirtual.gen.inc"
-#include "core/object/script_language.h"
 #include "core/variant/native_ptr.h"
 
 class PhysicsDirectSpaceState3D;

servers/rendering/shader_preprocessor.h

@@ -39,6 +39,7 @@
 #include "core/typedefs.h"
 
 #include "core/io/resource_loader.h"
+#include "core/object/script_language.h"
 #include "core/os/os.h"
 #include "scene/resources/shader.h"
 #include "scene/resources/shader_include.h"

servers/text/text_server_extension.h

@@ -32,7 +32,6 @@
 #define TEXT_SERVER_EXTENSION_H
 
 #include "core/object/gdvirtual.gen.inc"
-#include "core/object/script_language.h"
 #include "core/os/thread_safe.h"
 #include "core/variant/native_ptr.h"
 #include "core/variant/typed_array.h"