Statistics after Modify Column is not updated.

## Bug Report

Please answer these questions before submitting your issue. Thanks!

When modifying a column it does not update the statistics (here enum->varchar example)

### 1. Minimal reproduce step (Required)

```sql
drop table if exists t;
create table t (a int unsigned auto_increment primary key, b enum('a','b','c','d','e','f'));
insert into t (b) values ('a'),('b'),('c'),('d'),('e'),('f'),('a'),('d'),('f'),('f');
insert into t (b) select t.b from t,t t1,t t2,t t3;
select sleep(5);
analyze table t;
show stats_healthy;
select count(*) from t where b = 'f';
show stats_histograms where table_name = 't';
show stats_topn where table_name = 't';

alter table t modify column b varchar(25);
show stats_healthy;

select sleep(5);
select count(*) from t where b = 'f';
show stats_histograms where table_name = 't';
show stats_topn where table_name = 't';

analyze table t;
show stats_healthy;
select count(*) from t where b = 'f';
show stats_histograms where table_name = 't';
show stats_topn where table_name = 't';
```

### 2. What did you expect to see? (Required)

The histogram and TopN statistics reflecting the new column type.

### 3. What did you see instead (Required)

```sql
tidb> drop table if exists t;
Query OK, 0 rows affected, 1 warning (0.00 sec)

tidb> create table t (a int unsigned auto_increment primary key, b enum('a','b','c','d','e','f'));
Query OK, 0 rows affected (0.09 sec)

tidb> insert into t (b) values ('a'),('b'),('c'),('d'),('e'),('f'),('a'),('d'),('f'),('f');
Query OK, 10 rows affected (0.02 sec)
Records: 10 Duplicates: 0 Warnings: 0

tidb> insert into t (b) select t.b from t,t t1,t t2,t t3;
Query OK, 10000 rows affected (0.11 sec)
Records: 10000 Duplicates: 0 Warnings: 0

tidb> select sleep(5);
+----------+
| sleep(5) |
+----------+
| 0 |
+----------+
1 row in set (5.01 sec)

tidb> analyze table t;
Query OK, 0 rows affected, 1 warning (0.14 sec)

tidb> show stats_healthy;
+---------+------------+----------------+---------+
| Db_name | Table_name | Partition_name | Healthy |
+---------+------------+----------------+---------+
| test | t | | 100 |
+---------+------------+----------------+---------+
1 row in set (0.00 sec)

tidb> select count(*) from t where b = 'f';
+----------+
| count(*) |
+----------+
| 3003 |
+----------+
1 row in set (0.00 sec)

tidb> show stats_histograms where table_name = 't';
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time | Distinct_count | Null_count | Avg_col_size | Correlation | Load_status | Total_mem_usage | Hist_mem_usage | Topn_mem_usage | Cms_mem_usage |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
| test | t | | a | 0 | 2023-05-31 14:33:12 | 9990 | 0 | 8 | 1 | allEvicted | 0 | 0 | 0 | 0 |
| test | t | | b | 0 | 2023-05-31 14:33:12 | 6 | 0 | 8 | 0.13510223196468119 | allLoaded | 278 | 0 | 278 | 0 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
2 rows in set (0.00 sec)

tidb> show stats_topn where table_name = 't';
+---------+------------+----------------+-------------+----------+-------+-------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Value | Count |
+---------+------------+----------------+-------------+----------+-------+-------+
| test | t | | b | 0 | 1 | 2002 |
| test | t | | b | 0 | 2 | 1001 |
| test | t | | b | 0 | 3 | 1001 |
| test | t | | b | 0 | 4 | 2002 |
| test | t | | b | 0 | 5 | 1001 |
| test | t | | b | 0 | 6 | 3003 |
+---------+------------+----------------+-------------+----------+-------+-------+
6 rows in set (0.00 sec)

tidb>
tidb> alter table t modify column b varchar(25);
Query OK, 0 rows affected (1.22 sec)

--
-- Here the statistics look healthy
--
tidb> show stats_healthy;
+---------+------------+----------------+---------+
| Db_name | Table_name | Partition_name | Healthy |
+---------+------------+----------------+---------+
| test | t | | 100 |
+---------+------------+----------------+---------+
1 row in set (0.00 sec)

tidb>
tidb> select sleep(5);
+----------+
| sleep(5) |
+----------+
| 0 |
+----------+
1 row in set (5.00 sec)

tidb> select count(*) from t where b = 'f';
+----------+
| count(*) |
+----------+
| 3003 |
+----------+
1 row in set (0.04 sec)

tidb> show stats_histograms where table_name = 't';
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time | Distinct_count | Null_count | Avg_col_size | Correlation | Load_status | Total_mem_usage | Hist_mem_usage | Topn_mem_usage | Cms_mem_usage |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
| test | t | | a | 0 | 2023-05-31 14:33:12 | 9990 | 0 | 8 | 1 | allEvicted | 0 | 0 | 0 | 0 |
| test | t | | b | 0 | 2023-05-31 14:33:12 | 6 | 0 | 8 | 0.13510223196468119 | allLoaded | 278 | 0 | 278 | 0 |
| test | t | | b | 0 | 2023-05-31 14:33:13 | 0 | 10010 | 0 | 0 | allLoaded | 0 | 0 | 0 | 0 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
3 rows in set (0.00 sec)

--
-- Here it is still the old enum values instead of the 'a'-'f' varchar's!
--
tidb> show stats_topn where table_name = 't';
+---------+------------+----------------+-------------+----------+-------+-------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Value | Count |
+---------+------------+----------------+-------------+----------+-------+-------+
| test | t | | b | 0 | 1 | 2002 |
| test | t | | b | 0 | 2 | 1001 |
| test | t | | b | 0 | 3 | 1001 |
| test | t | | b | 0 | 4 | 2002 |
| test | t | | b | 0 | 5 | 1001 |
| test | t | | b | 0 | 6 | 3003 |
+---------+------------+----------------+-------------+----------+-------+-------+
6 rows in set (0.00 sec)

tidb>
tidb> analyze table t;
Query OK, 0 rows affected, 1 warning (0.19 sec)

tidb> show stats_healthy;
+---------+------------+----------------+---------+
| Db_name | Table_name | Partition_name | Healthy |
+---------+------------+----------------+---------+
| test | t | | 100 |
+---------+------------+----------------+---------+
1 row in set (0.00 sec)

tidb> select count(*) from t where b = 'f';
+----------+
| count(*) |
+----------+
| 3003 |
+----------+
1 row in set (0.01 sec)

tidb> show stats_histograms where table_name = 't';
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time | Distinct_count | Null_count | Avg_col_size | Correlation | Load_status | Total_mem_usage | Hist_mem_usage | Topn_mem_usage | Cms_mem_usage |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
| test | t | | a | 0 | 2023-05-31 14:33:18 | 9990 | 0 | 8 | 1 | allEvicted | 0 | 0 | 0 | 0 |
| test | t | | b | 0 | 2023-05-31 14:33:12 | 6 | 0 | 8 | 0.13510223196468119 | allLoaded | 278 | 0 | 278 | 0 |
| test | t | | b | 0 | 2023-05-31 14:33:18 | 6 | 0 | 2 | 0.13510223196468119 | allLoaded | 284 | 0 | 284 | 0 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+---------------------+-------------+-----------------+----------------+----------------+---------------+
3 rows in set (0.00 sec)

--
-- And here after a manual ANALYZE TABLE, the old enum values are still there!
--
tidb> show stats_topn where table_name = 't';
+---------+------------+----------------+-------------+----------+-------+-------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Value | Count |
+---------+------------+----------------+-------------+----------+-------+-------+
| test | t | | b | 0 | 1 | 2002 |
| test | t | | b | 0 | 2 | 1001 |
| test | t | | b | 0 | 3 | 1001 |
| test | t | | b | 0 | 4 | 2002 |
| test | t | | b | 0 | 5 | 1001 |
| test | t | | b | 0 | 6 | 3003 |
| test | t | | b | 0 | a | 2002 |
| test | t | | b | 0 | b | 1001 |
| test | t | | b | 0 | c | 1001 |
| test | t | | b | 0 | d | 2002 |
| test | t | | b | 0 | e | 1001 |
| test | t | | b | 0 | f | 3003 |
+---------+------------+----------------+-------------+----------+-------+-------+
12 rows in set (0.00 sec)
```

No updated statistics. And after manual `analyze table t` the old statistics is still there!

Also if there would be an index on 'b' it seems like the statistics would been updated after the `alter table`.

### 4. What is your TiDB version? (Required)

```
tidb_version(): Release Version: v7.2.0-alpha
Edition: Community
Git Commit Hash: 65d5ef2eaa34c17e73928d17be339b8dbdcddc11
Git Branch: heads/refs/tags/v7.2.0-alpha
UTC Build Time: 2023-05-31 02:32:36
GoVersion: go1.20.3
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: tikv
```