🙏选中多个单元格时，可以配置开启不显示内部描边，只展示选中区域整体的外部描边

### 🏷 Version

| Package | Version |
| -------------- | ------- |
| @antv/s2 | 1.54.1 |
| @antv/s2-react | 1.46.0 |
| @antv/s2-vue | - |

### Sheet Type

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

### 🖋 Description

### 选中多个单元格时，可以配置开启不显示内部的描边
目前 s2 可以配置选中的数据单元格激活状态为描边
```
theme: {
dataCell: {
cell: {
interactionState: {
selected: {
borderWidth: 1,
borderColor: '#000',
borderOpacity: 1,
},
},
},
},
},
```
展示样式为：

选中区域内部单元格会有两层黑色边框，希望可以支持配置成不展示中间的边框，类似下面 excel 效果：

### 🧐 Suggest the API

theme - dataCell 可以配置 inner boarder 关闭/样式

| name | type | default | description |
| ---- | ---- | ------- | ----------- |
| - | - | - | - |

Start by locating the dataCell theme configuration and the selected interaction-state rendering used by PivotSheet and TableSheet. Check how the current borderWidth, borderColor, and borderOpacity settings are applied across adjacent selected cells. Done means a configuration can hide internal borders while preserving the outer border, with coverage for multi-cell selection.

Written by the indexing model from the issue text.