Allow setting CGUISize properties directly

Previously, modifying individual CGUISize properties (left, top, right,
bottom) via JavaScript had no effect unless the entire size object was
copied, modified, and reassigned—resulting in verbose and error-prone
code.

This update introduces proper JavaScript property accessors, enabling
direct reading and writing of CGUISize members. The result is a more
intuitive and scriptable API.

Key Changes:
- Implemented JavaScript get/set accessors for each CGUISize property,
  directly interacting with the native object.
- Retained support for string assignments to CGUISize
- Maintained the GUISize JS object for backward compatibility, also
  marked as deprecated.
- Improved CGUISimpleSetting<CGUISize> to allow partial updates via
  direct property access.
- allow assigning size from object with pixel and percent values

You can now assign size using an object with properties like:
size = {
  left: number, right: number, top: number, bottom: number,
  rleft: number, rright: number, rtop: number, rbottom: number
}

- One or more properties can be specified, the missing properties with
  fill as zero.
- Assignment triggers an immediate update event.

Delayed Setting Notifications:
- Introduced a mechanism for delayed setting notifications, currently
  only used in CGUISimpleSetting<CGUISize>, to avoid redundant
  recalculations.
- Ensured that getComputedSize triggers any pending delayed
  notifications before returning the size.

This change significantly enhances the developer experience and brings
the behavior in line with typical expectations for direct property
manipulation in JavaScript.

source/gui/Scripting/ScriptFunctions.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -20,6 +20,7 @@
 #include "ScriptFunctions.h"
 
 #include "graphics/scripting/JSInterface_GameView.h"
+#include "gui/Scripting/JSInterface_CGUISize.h"
 #include "gui/Scripting/JSInterface_GUIManager.h"
 #include "gui/Scripting/JSInterface_GUISize.h"
 #include "i18n/scripting/JSInterface_L10n.h"
@@ -53,6 +54,7 @@ void GuiScriptingInit(ScriptInterface& scriptInterface)
 	ScriptRequest rq(scriptInterface);
 
 	JSI_GUISize::RegisterScriptClass(scriptInterface);
+	JSI_CGUISize::RegisterScriptClass(scriptInterface);
 	JSI_ConfigDB::RegisterScriptFunctions(rq);
 	JSI_Console::RegisterScriptFunctions(rq);
 	JSI_Debug::RegisterScriptFunctions(rq);