Move random test util code from setup_common to random

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

src/test/validation_block_tests.cpp

@@ -11,6 +11,7 @@
 #include <pow.h>
 #include <random.h>
 #include <script/standard.h>
+#include <test/util/random.h>
 #include <test/util/script.h>
 #include <test/util/setup_common.h>
 #include <util/time.h>