Function create_block_template 

pub fn create_block_template(
    utxo_set: &UtxoSet,
    mempool_txs: &[Transaction],
    height: Natural,
    prev_header: &BlockHeader,
    prev_headers: &[BlockHeader],
    coinbase_script: &ByteString,
    coinbase_address: &ByteString,
) -> Result<BlockTemplate>

Create a block template for mining