🐛 [Enhancement] 桑基图数据量过多时，如何展示

### 🐛 Bug description [Please make everyone to understand it]
数据过多时，桑基图不能展示连线。截图中大约为700条记录。

### 💻 Link to minimal reproduction

https://codesandbox.io/s/sankey-demo-myeqh?file=/index.ts

### 📷 Step to reproduce
（1）打开链接。
（2）用准备好的数据，替换示例的数据集

### 🏞 Expected result
桑基图正常展示连线

### 🚑 Any additional [like screenshots]

* **G2Plot Version**:
* **Platform**:

Start with the linked CodeSandbox reproduction, particularly index.ts, and replace the sample dataset with the prepared data containing about 700 records. Observe how the Sankey chart handles the larger dataset and compare it with the expected result: all connecting lines should render normally.

Written by the indexing model from the issue text.