add a method to compute transaction hashes

[tdelabro]

Blockifier transaction types are build ontop of starknet API ones and require you to provide the transaction hash.
The tx hash can be computed based on the tx if you add the chain_id and boolean signaling if you need to offset the version number. You also can make it generic over a hashing function.

This logic should be implemented as a trait on every transaction type

trait ComputeTransactionHash {
  fn compute_hash<H: HasherT>(&self, chain_id: Starkfelt, offset_version: bool) -> TransactionHash;
}

This would avoid every lib consumer to reimplement this logic themselves everytime