🤔透视表列头和行头能够满足某些特殊的合并单元格的需求吗？

### 🏷 Version
| Package | Version |
| -------------- | ------- |
| @antv/s2 | 1.51.2 |
| @antv/s2-react | |
| @antv/s2-vue | |

### Sheet Type

- [x] PivotSheet
- [ ] TableSheet
- [ ] GridAnalysisSheet
- [ ] StrategySheet
- [ ] EditableSheet

### 🖋 Description

如上图所示，
行维度： ["省份","城市","阶段"]
列维度: ["指标大类","指标小类"]
### 😊 Expected Behavior
我期望可以在顶部列头合并特殊需求的单元格。
### 😅 Current Behavior
没法合并。因为列维度有两个，所以总量那个单元格没法合并。
返回的值类似:
{ province:"山东",city:"日照",period:"本期",measureGroup1:"总量1(去重)",measureGroup2:"总量1(去重)",count:1,peopleCount:2},
{ province:"山东",city:"日照",period:"同期",measureGroup1:"总量1(去重)",measureGroup2:"总量1(去重)",count:1,peopleCount:2}

Start by reproducing the case in PivotSheet with the stated province, city, period, and measure dimensions and the sample records. Read the column-header rendering and merge behavior in the @antv/s2 package, then verify that the special top header can merge without breaking the remaining column headers.

Written by the indexing model from the issue text.