`actRows` of DML statements is always 0

## Enhancement
As you can see below, `actRows` of DML statements is always 0, which is confused:
```
mysql> explain analyze insert into t values (55);
+----------+---------+---------+------+---------------+----------------------------------------------------------+---------------+----------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------+---------+---------+------+---------------+----------------------------------------------------------+---------------+----------+------+
| Insert_1 | N/A | 0 | root | | time:120.6µs, loops:1, prepare: 63.4µs, insert:57.2µs | N/A | 97 Bytes | N/A |
+----------+---------+---------+------+---------------+----------------------------------------------------------+---------------+----------+------+
1 row in set (0.00 sec)

mysql> explain analyze replace into t values (5), (29);
+----------+---------+---------+------+---------------+-------------------------------------------------------------------------------------------+---------------+-----------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------+---------+---------+------+---------------+-------------------------------------------------------------------------------------------+---------------+-----------+------+
| Insert_1 | N/A | 0 | root | | time:187µs, loops:1, prefetch: 120.5µs, rpc: {BatchGet:{num_rpc:1, total_time:45.3µs}} | N/A | 144 Bytes | N/A |
+----------+---------+---------+------+---------------+-------------------------------------------------------------------------------------------+---------------+-----------+------+
1 row in set (0.00 sec)
```