feat: ion-item: detailIcon as entry in global ionic config

### 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 isn't a clear way to re-define the chevron icon globally in ion-item; adding that to IonicConfig would solve this issue.

### Describe the Use Case

Theming, mostly.

### Describe Preferred Solution

_No response_

### Describe Alternatives

_No response_

### Related Code

_No response_

### Additional Information

_No response_

Start by locating the ion-item component and the IonicConfig definition. Trace how the chevron/detail icon is selected and how global configuration values are consumed. Done means detailIcon can be set through IonicConfig and ion-item uses that global value for its chevron, with behavior covered by the project's relevant tests.

Written by the indexing model from the issue text.