[Feature] Integrate Steel with a block history service

[nategraf]

One of the common challenges with using Steel today is linking your proof to a block that is part of the target chain (e.g. by using the blockhash builtin). With support for EIP-4788 commitments, we can support no-cost linking for up to ~24 hours. Linking back more than 24 hours requires one of the strategies discussed in the Steel README.

A powerful solution would be to integrate with a block history service that assembles the hash chain into an efficiently query-able structure, such as a Merkle tree. With this, we could provide linking to any block in the chain with a low upper bound of work: just verifying a Merkle inclusion proof.