Fix exit table, set delayed_withdrawn in exits

- In exit table, `instant_withdrawn`, `delayed_withdraw_request`, and
  `delayed_withdrawn` were referencing batch_num.  But these actions happen
  outside a batch, so they should reference a block_num.
- Process delayed withdrawns:
    - In Synchronizer, first match a Rollup delayed withdrawn request, with the
      WDelayer deposit (via TxHash), and store the owner and token associated
      with the delayed withdrawn.
    - In HistoryDB: store the owner and token of a delayed withdrawal request
      in the exit_tree, and set delayed_withdrawn when the withdraw is done in
      the WDelayer.
- Update dependency of sqlx to master
    - Last release of sqlx is from 2018 October, and it doesn't support
      `NamedQuery` with a slice of structs, which is used in this commit.

eth/rollup.go

@@ -91,6 +91,7 @@ type RollupEventWithdraw struct {
 	Idx             uint64
 	NumExitRoot     uint64
 	InstantWithdraw bool
+	TxHash          ethCommon.Hash // Hash of the transaction that generated this event
 }
 
 // RollupEvents is the list of events in a block of the Rollup Smart Contract
@@ -577,6 +578,7 @@ func (c *RollupClient) RollupEventsByBlock(blockNum int64) (*RollupEvents, *ethC
 			if instantWithdraw == 1 {
 				withdraw.InstantWithdraw = true
 			}
+			withdraw.TxHash = vLog.TxHash
 			rollupEvents.Withdraw = append(rollupEvents.Withdraw, withdraw)
 		}
 	}