message: refactor: Avoid defining const in two places
  Pass the allocated column to util/avl instead of re-declare the column const in the crate.
diff: @@ -17,7 +17,7 @@ use std::ops::Deref;
  use std::ops::Range;
  use {
  COLUMN_BLOCK_BODY, COLUMN_BLOCK_HEADER, COLUMN_BLOCK_TRANSACTION_ADDRESSES, COLUMN_BLOCK_UNCLE,
  - COLUMN_EXT, COLUMN_OUTPUT_ROOT,
  + COLUMN_EXT, COLUMN_OUTPUT_ROOT, COLUMN_TRANSACTION_META,
  };
  pub struct ChainKVStore<T: KeyValueDB> {
  @@ -145,7 +145,7 @@ impl<T: KeyValueDB> ChainStore for ChainKVStore<T> {
  }
  fn get_transaction_meta(&self, root: H256, key: H256) -> Option<TransactionMeta> {
  - search(&self.db, root, key).expect("tree operation error")
  + search(&self.db, COLUMN_TRANSACTION_META, root, key).expect("tree operation error")
  }
  fn get_output_root(&self, block_hash: &H256) -> Option<H256> {
  @@ -158,7 +158,7 @@ impl<T: KeyValueDB> ChainStore for ChainKVStore<T> {
  root: H256,
  cells: Vec<(Vec<OutPoint>, Vec<OutPoint>)>,
  ) -> Option<H256> {
  - let mut avl = AvlTree::new(&self.db, root);
  + let mut avl = AvlTree::new(&self.db, COLUMN_TRANSACTION_META, root);
  for (inputs, outputs) in cells {
  for input in inputs {
  