test: refactor, decouple HasReason from test framework machinery

Avoid providing the entire unit test framework dependency to tests that only
require access to the HasReason utility class.

E.g. reverselock_tests.cpp, sync_tests.cpp, util_check_tests.cpp, util_string_tests.cpp,
and script_parse_tests.cpp only require access to HasReason and nothing else.

src/test/httpserver_tests.cpp

@@ -3,6 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <httpserver.h>
+#include <test/util/common.h>
 #include <test/util/setup_common.h>
 
 #include <boost/test/unit_test.hpp>