message: [miner] update TxPool.
diff: @@ -9,7 +9,7 @@ use storage::{memory_storage::MemoryStorage, StarcoinStorage};
  use sync::{DownloadActor, ProcessActor, SyncActor};
  use tokio::time::{delay_for, Duration};
  use traits::{AsyncChain, TxPoolAsyncService};
  -use txpool::{TxPoolActor, TxPoolRef};
  +use txpool::{CachedSeqNumberClient, TxPool, TxPoolActor, TxPoolRef};
  use types::{peer_info::PeerInfo, transaction::SignedUserTransaction};
  #[test]
  @@ -24,7 +24,8 @@ async fn test_miner_with_schedule_pacemaker() {
  let bus = BusActor::launch();
  let repo = Arc::new(MemoryStorage::new());
  let storage = Arc::new(StarcoinStorage::new(repo).unwrap());
  - let txpool = TxPoolActor::launch(config.clone(), bus.clone(), storage.clone()).unwrap();
  + let seq_number_client = CachedSeqNumberClient::new(storage.clone());
  + let txpool = TxPool::start(seq_number_client);
  let chain = ChainActor::launch(config.clone(), storage.clone()).unwrap();
  let _miner =
  MinerActor::<DummyConsensus, MockExecutor, TxPoolRef, ChainActorRef<ChainActor>>::launch(
  @@ -40,7 +41,7 @@ async fn test_miner_with_schedule_pacemaker() {
  DownloadActor::launch(peer_info, chain.clone()).expect("launch DownloadActor failed.");
  let sync = SyncActor::launch(bus, process_actor, download_actor).unwrap();
  - for _i in 0..5 {
  + for _i in 0..5 as usize {
  txpool
  .clone()
  .add(SignedUserTransaction::mock())
  