🐛 明细表冻结列中无法合并单元格

### 🏷 Version

| Package | Version |
| -------------- | --------- |
| @antv/s2 | latest |
| @antv/s2-react | |
| @antv/s2-vue | 1.0.1 |

### Sheet Type

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

### 🖋 Description

通过 frozenColCount 设置冻结列后，冻结列中原本合并的单元格失效

### ⌨️ Code Snapshots

```javascript
const s2Options = {
width: 400,
height: 400,
frozenColCount: 2,
mergedCellsInfo: [
[
{ colIndex: 0, rowIndex: 0, showText: true },
{ colIndex: 0, rowIndex: 1 },
{ colIndex: 0, rowIndex: 2 },
{ colIndex: 0, rowIndex: 3 },
{ colIndex: 0, rowIndex: 4 },
],
],
}
```

### 🔗 Reproduce Link

https://codesandbox.io/s/admiring-haze-s1dw9f

### 🤔 Steps to Reproduce

同时对左侧第一列设置 frozenColCount 和 mergedCellsInfo

### 😊 Expected Behavior

冻结列中展示合并的单元格

### 😅 Current Behavior

冻结列中无法展示合并的单元格

### 💻 System information