Exclude empty requests data in commitment (EIP-7685)

Apply the [EIP-7685 update] included in [pectra-devnet-5].

[EIP-7685 update]: ethereum/EIPs#8989
[pectra-devnet-5]: https://notes.ethereum.org/@ethpandaops/pectra-devnet-5

Author: chfast

test/state/requests.cpp

@@ -20,9 +20,8 @@ hash256 calculate_requests_hash(std::span<const Requests> block_requests_list)
 
     for (const auto& requests : block_requests_list)
     {
-        // TODO recent change in the spec, uncomment for devnet-5
-        //        if (requests.data.empty())
-        //            continue;
+        if (requests.data().empty())
+            continue;  // Skip empty requests.
 
         hash256 requests_hash;
         crypto::sha256(reinterpret_cast<std::byte*>(requests_hash.bytes),