feat(reflect-cpp): Switched from glaze -> reflect cpp

A bug was discovered in glaze which prevented valid toml output. We have
switched to toml++ and reflect-cpp. The interface has remained the same
so this should not break any code

build-config/reflect-cpp/include/rfl/internal/is_flatten_field.hpp

@@ -0,0 +1,27 @@
+#ifndef RFL_INTERNAL_ISFLATTENFIELD_HPP_
+#define RFL_INTERNAL_ISFLATTENFIELD_HPP_
+
+#include <type_traits>
+
+#include "../Flatten.hpp"
+
+namespace rfl {
+namespace internal {
+
+template <class T>
+class is_flatten_field;
+
+template <class T>
+class is_flatten_field : public std::false_type {};
+
+template <class T>
+class is_flatten_field<Flatten<T>> : public std::true_type {};
+
+template <class T>
+constexpr bool is_flatten_field_v =
+    is_flatten_field<std::remove_cvref_t<std::remove_pointer_t<T>>>::value;
+
+}  // namespace internal
+}  // namespace rfl
+
+#endif