feat: Ion-datetime wheel focused column to be styled with CSS

### Prerequisites

- [x] I have read the [Contributing Guidelines](https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#creating-an-issue).
- [x] I agree to follow the [Code of Conduct](https://ionicframework.com/code-of-conduct).
- [x] I have searched for [existing issues](https://github.com/ionic-team/ionic-framework/issues) that already include this feature request, without success.

### Describe the Feature Request

- Have a way to style the focused column of an ion-datetime wheel (`preferWheel="true"`).

### Describe the Use Case

- When toggling the different sections of the datetime wheel with the keyboard, we're unable to style the focused element (wheel column), and there is currently no documentation or guide on how to do this


### Describe Preferred Solution

_No response_

### Describe Alternatives

_No response_

### Related Code

_No response_

### Additional Information

_No response_

首先查看与此 issue 关联的已关闭且已合并的 pull request #30934，以及它所处理的 ion-datetime 滚轮行为。确认是否可以通过现有组件表面对获得焦点的列进行样式设置；完成标准是：对于通过键盘获得焦点的滚轮列，存在一条有文档记录且可验证的样式设置路径。

由索引模型根据 Issue 内容生成。