feature reqeust: add data_hash to batch API

[lispc]

why:

batch pi_hash is calculated in rust/golang/solidity. In case there is any inconsistency, having this field inside API can help debugging. For example, currently in circuit side, we fetch fetch all blocks inside a batch and proving the batch, but cannot constrain the batch pi == batch pi calculated by other components(coordinator, contracts). So exposing data_hash is useful.