feat: Make Datetime emit the working parts of the date

### 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

There should be an ion-datetime event that gets fired whenever someone commits changes to the month, year, et cetera.

### Describe the Use Case

Some people may want to highlight days per-month in the month view. Currently, one has to submit an entire list of dots for every entry they want to highlight, which is resource intensive with large data sets.

Narrowing the view to the month the person is currently viewing would make this process faster.

### Describe Preferred Solution

an `ionPeek` event with `event.detail.parts` that would include the object that is in `this.workingParts`.

### Describe Alternatives

_No response_

### Related Code

_No response_

### Additional Information

_No response_

首先定位 ion-datetime 的实现以及请求中引用的 workingParts 状态。跟踪月份和年份变更的提交方式，然后定义围绕这些变更的事件行为，并验证其 detail 会公开 working date parts，而不要求提供完整的高亮日期列表。

由索引模型根据 Issue 内容生成。