🤔 [QUESTION]双轴图meta设置alias，字段名含有点.号时不生效？

### 🐛 Question description [Please make everyone to understand it]
在双轴图中，用`meta`设置`alias`时，若字段名含有`.`号时，图表标识位置不生效。

### 💻 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**:

Start with the linked g2plot reproduction template and reproduce the dual-axis chart using meta.alias with a field name containing a period. Compare the displayed chart identifier with the expected alias; the issue is complete when the alias takes effect for dotted field names in a minimal reproduction.

Written by the indexing model from the issue text.