Move random test util code from setup_common to random

as many of the unit tests don't use this code

src/wallet/test/wallet_crypto_tests.cpp

@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <test/util/random.h>
 #include <test/util/setup_common.h>
 #include <util/strencodings.h>
 #include <wallet/crypter.h>