test: Use std::bit_cast (#712)

Author: chfast

test/state/hash_utils.hpp

@@ -7,7 +7,7 @@
 #include <ethash/keccak.hpp>
 #include <evmc/evmc.hpp>
 #include <evmc/hex.hpp>
-#include <cstring>
+#include <bit>
 
 namespace evmone
 {
@@ -29,10 +29,7 @@ static constexpr auto EmptyListHash =
 /// Computes Keccak hash out of input bytes (wrapper of ethash::keccak256).
 inline hash256 keccak256(bytes_view data) noexcept
 {
-    const auto eh = ethash::keccak256(data.data(), data.size());
-    hash256 h;
-    std::memcpy(h.bytes, eh.bytes, sizeof(h));  // TODO: Use std::bit_cast.
-    return h;
+    return std::bit_cast<hash256>(ethash::keccak256(data.data(), data.size()));
 }
 }  // namespace evmone