message: [mempool] clean up internals of TxnsLog
diff: @@ -13,32 +13,26 @@ use serde::Serialize;
  use std::fmt;
  pub struct TxnsLog {
  - txns: Vec<(AccountAddress, u64)>,
  - status: Vec<String>,
  + txns: Vec<(AccountAddress, u64, Option<String>)>,
  }
  impl TxnsLog {
  pub fn new() -> Self {
  - Self {
  - txns: vec![],
  - status: vec![],
  - }
  + Self { txns: vec![] }
  }
  pub fn new_txn(account: AccountAddress, seq_num: u64) -> Self {
  Self {
  - txns: vec![(account, seq_num)],
  - status: vec![],
  + txns: vec![(account, seq_num, None)],
  }
  }
  pub fn add(&mut self, account: AccountAddress, seq_num: u64) {
  - self.txns.push((account, seq_num));
  + self.txns.push((account, seq_num, None));
  }
  pub fn add_with_status(&mut self, account: AccountAddress, seq_num: u64, status: &str) {
  - self.add(account, seq_num);
  - self.status.push(status.to_string());
  + self.txns.push((account, seq_num, Some(status.to_string())));
  }
  }
  @@ -46,9 +40,9 @@ impl fmt::Display for TxnsLog {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  let mut txns = "".to_string();
  - for (idx, (account, seq_num)) in self.txns.iter().enumerate() {
  + for (account, seq_num, status) in self.txns.iter() {
  let mut txn = format!("{}:{}", account, seq_num);
  - if let Some(status) = self.status.get(idx) {
  + if let Some(status) = status {
  txn += &format!(":{}", status)
  }
  