Function create_block_template 

pub fn create_block_template(
    utxo_set: &HashMap<OutPoint, Arc<UTXO>, FxBuildHasher>,
    mempool_txs: &[Transaction],
    height: u64,
    prev_header: &BlockHeader,
    prev_headers: &[BlockHeader],
    coinbase_script: &Vec<u8>,
    coinbase_address: &Vec<u8>,
) -> Result<BlockTemplate, ConsensusError>

Create a block template for mining