EnumUtils: Add Common::ToUnderlying

Mirrors the C++23 <utility> function, std::to_underlying

Source/Core/Common/EnumUtils.h

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: CC0-1.0
+
+#pragma once
+
+#include <type_traits>
+
+namespace Common
+{
+// TODO: Replace with std::to_underlying in C++23
+template <typename Enum>
+constexpr std::underlying_type_t<Enum> ToUnderlying(Enum e) noexcept
+{
+  return static_cast<std::underlying_type_t<Enum>>(e);
+}
+}  // namespace Common