Fix most headers in gui

Make include-what-you-use happy with most of the files in source/gui and
fix what needs to be fixed after including missing compile flags.

Ref: #8086
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>

source/gui/GUIObjectTypes.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 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
@@ -36,6 +36,13 @@
 #include "gui/ObjectTypes/CText.h"
 #include "gui/ObjectTypes/CTooltip.h"
 #include "gui/Scripting/JSInterface_GUIProxy.h"
+#include "ps/CStr.h"
+
+#include <memory>
+#include <unordered_map>
+#include <utility>
+
+class IGUIObject;
 
 void CGUI::AddObjectTypes()
 {