Add util/types.h with ALWAYS_FALSE template

src/util/types.h

@@ -0,0 +1,11 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_TYPES_H
+#define BITCOIN_UTIL_TYPES_H
+
+template <class>
+inline constexpr bool ALWAYS_FALSE{false};
+
+#endif // BITCOIN_UTIL_TYPES_H