Reorganized core/ directory, it was too fatty already

-Removed FuncRef, since Callable makes it obsolete
-Removed int_types.h as its obsolete in c++11+
-Changed color names code

modules/gdscript/language_server/gdscript_extend_parser.h

@@ -32,7 +32,7 @@
 #define GDSCRIPT_EXTEND_PARSER_H
 
 #include "../gdscript_parser.h"
-#include "core/variant.h"
+#include "core/variant/variant.h"
 #include "lsp.hpp"
 
 #ifndef LINE_NUMBER_TO_INDEX