🐛 [BUG] 多图层图表，图例legend设置selected不生效

### 🐛 Bug description [Please make everyone to understand it]
在多图层图标的图例legend中，添加selected属性不生效
> Please provide a link by forking these links [G2Plot](https://codesandbox.io/s/g2plot-issue-template-gzfdq?file=/index.ts) or GitHub repo, a minimal reproduction.
https://codesandbox.io/s/p4lmfj?file=/index.ts
* _Required_ **Link to minimal reproduction**:

### 📷 Step to reproduce

### 🏞 Expected result

### 🚑 Any additional [like screenshots]

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

Start with index.ts in the linked CodeSandbox reproduction and verify the multi-layer chart's legend configuration, especially the selected property. Trace how that configuration is applied when the chart renders. Done means the selected setting takes effect in the reproduction and the legend displays the expected layer state.

Written by the indexing model from the issue text.