🤔 [QUESTION]是否考虑图例中新增全选/反选

### 🐛 Question description [Please make everyone to understand it]

### 💻 Link to minimal reproduction

Please provide a link by forking these links [g2plot](https://codesandbox.io/s/g2plot-reproduction-template-gyej1) or GitHub repo. What is a minimal reproduction, and why is it required?

### 🏞 Expected result

### 🚑 Any additional [like screenshots]

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

The issue names no files, tests, or entry points and provides no reproduction or expected result. First clarify whether legend selection should support select-all, invert-selection, or both, then identify the affected chart components and define expected behavior before implementation.

Written by the indexing model from the issue text.