Prefer std::array over C-style array in base_uint

src/test/basics/base_uint_test.cpp

@@ -22,6 +22,8 @@
 #include <ripple/beast/unit_test.h>
 #include <boost/algorithm/string.hpp>
 
+#include <type_traits>
+
 namespace ripple {
 namespace test {
 
@@ -50,6 +52,8 @@ struct nonhash
 struct base_uint_test : beast::unit_test::suite
 {
     using test96 = base_uint<96>;
+    static_assert(std::is_copy_constructible<test96>::value, "");
+    static_assert(std::is_copy_assignable<test96>::value, "");
 
     void run() override
     {