Use AncestralClass to speed up Object::cast_to when possible.

core/object/script_language.h

@@ -140,6 +140,8 @@ protected:
 	}
 
 public:
+	static constexpr AncestralClass static_ancestral_class = AncestralClass::SCRIPT;
+
 	virtual void reload_from_file() override;
 
 	virtual bool can_instantiate() const = 0;