fix(partition): 分区表index merge查询 · Pull Request !444 · openEuler/cantian-connector-mysql

**[Background]**
问题场景：
```
CREATE TABLE `t2` (
  id int,
  a int,
  b int,
  KEY `idx_a` (a),
  KEY `idx_b` (b)
)
PARTITION BY RANGE (`id`)
(PARTITION p0 VALUES LESS THAN (10) ENGINE = CTC,
PARTITION p1 VALUES LESS THAN (20) ENGINE = CTC,
PARTITION p2 VALUES LESS THAN (30) ENGINE = CTC,
PARTITION p4 VALUES LESS THAN MAXVALUE ENGINE = CTC);
insert into t2  values(30, 2, 3), (20, 1, 3), (10, 1, 3);
select /*+ INDEX_MERGE(t2 idx_a, idx_b) */ count(*) from t2 where a = 1 and b = 3; # 查询结果不一致
```

**[Root Cause]**
分区表`ha_ctcpart::cmp_ref`接口和`m_queue->m_fun(ha_ctcpart::key_and_rowid_cmp)`未对接，导致`rowid`比较错误。
其中，
- `m_queue->m_fun`会预先将每个分区取出的数据进行排序，以方便每个队列按顺序交叉比较。
- `ha_ctcpart::cmp_ref`同`ha_ctc::cmp_ref`，是比较`rowid`的直接接口，前两个字节为分区信息，需要跳过，从第三个字节开始为`rowid`。

**[Changes Made]**
新增分区表中比较`rowid`接口`ha_ctcpart::cmp_ref`接口和`m_queue->m_fun`。
修改后上述用例流程如下：
```
# handler1: 使用idx_a (a = 1)
ha_ctcpart::position_in_last_part 0x7f194c57b3f8
--> ctc_position(part_id = 2) {file = 15, page = 164, slot = 0, unused2 = 0} --> rowid3
ha_ctcpart::position_in_last_part 0x7f194c57b3f8
--> ctc_position(part_id = 3) {file = 15, page = 28, slot = 0, unused2 = 0}  --> rowid2

# handler1: 排序
ha_ctcpart::key_and_rowid_cmp
--> rowid2 < rowid3

# handler2: 使用idx_b (b = 3)
ha_ctcpart::position_in_last_part 0x7f194c5c8a58
--> ctc_position(part_id = 1) {file = 15, page = 20, slot = 0, unused2 = 0}  --> rowid1
ha_ctcpart::position_in_last_part 0x7f194c5c8a58
--> ctc_position(part_id = 2) {file = 15, page = 164, slot = 0, unused2 = 0} --> rowid3
ha_ctcpart::position_in_last_part 0x7f194c5c8a58
--> ctc_position(part_id = 3) {file = 15, page = 28, slot = 0, unused2 = 0}  --> rowid2

# handler2: 排序
ha_ctcpart::key_and_rowid_cmp
--> rowid1 < rowid2 < rowid3

# 比较
ha_ctcpart::cmp_ref (cmp = -1)
--> rowid1 (part_id = 1) {file = 15, page = 20, slot = 0, unused2 = 0}
--> rowid2 (part_id = 2) {file = 15, page = 28, slot = 0, unused2 = 0}

ha_ctcpart::cmp_ref (cmp = 0, cnt++)
--> rowid2 (part_id = 2) {file = 15, page = 28, slot = 0, unused2 = 0}
--> rowid2 (part_id = 2) {file = 15, page = 28, slot = 0, unused2 = 0}

ha_ctcpart::cmp_ref (cmp = 0, cnt++)
--> rowid3 (part_id = 3) {file = 15, page = 164, slot = 0, unused2 = 0}
--> rowid3 (part_id = 3) {file = 15, page = 164, slot = 0, unused2 = 0}
```

**[Test Result]**
![输入图片说明](https://foruda.gitee.com/images/1733986317297204545/6d9d6ba0_10133320.png "屏幕截图")

类型	指派人员	状态
审查	openeuler-ci-bot	已完成 (0/0人)
测试	openeuler-ci-bot	已完成 (0/0人)

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