Replace SFINAE with concepts (#5361)

Concepts are cleaner to use and result in much better error messages for incorrect template use.

wpiutil/src/main/native/include/wpi/DecayedDerivedFrom.h

@@ -0,0 +1,18 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <type_traits>
+
+#include "wpi/concepts.h"
+
+namespace wpi {
+
+template <class Derived, class Base>
+concept DecayedDerivedFrom =
+    std::derived_from<std::decay_t<Derived>, std::decay_t<Base>> &&
+    std::convertible_to<std::decay_t<Derived>*, std::decay_t<Base>*>;
+
+}  // namespace wpi