Move random test util code from setup_common to random

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

src/test/miner_tests.cpp

@@ -9,6 +9,7 @@
 #include <node/miner.h>
 #include <policy/policy.h>
 #include <script/standard.h>
+#include <test/util/random.h>
 #include <test/util/txmempool.h>
 #include <timedata.h>
 #include <txmempool.h>