🧐[问题] protable columns 分组后，子级字段怎么出现在搜索条件中

### 🧐 问题描述
protable columns 分组后，子级字段怎么出现在搜索条件中, 如下面示例代码，我想要test1,test2,test3为搜索条件怎么实现

### 💻 示例代码
```
pro_columns = [
{
title: 'Basic Information',
search: false,
children: [
{
title: 'test1',
key: 'test1',
dataIndex: 'test1',
fixed: 'left',
width: '10%',
},
{
title: 'test2',
key: 'test2',
dataIndex: 'test2',
fixed: 'left',
width: '10%',
},
{
title: 'test3',
key: 'test3',
dataIndex: 'test3',
width: '10%',
},
{
title: 'test4',
key: 'test4',
dataIndex: 'test4',
search: false,
},
],
},
]
```

### 🚑 其他信息

Start by reproducing the reported ProTable configuration with the grouped columns in the issue, focusing on how child fields are converted into search conditions. The work is done when test1, test2, and test3 appear as searchable fields while test4 remains excluded by search: false.

Written by the indexing model from the issue text.