feat: Override default ion-breadcrumbs collapsed indicator

### 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

Adding option to overwrite the default collapsed indicator button for `ion-breadcrumbs`

### Describe the Use Case

It lets users change the default `ion-breadcrumbs` collapsing indicator button

### Describe Preferred Solution

```html

```

### Describe Alternatives

_No response_

### Related Code

_No response_

### Additional Information

_No response_

Start at the ion-breadcrumbs component and inspect how maxItems and the current collapsed indicator are handled. Done means consumers can provide a custom collapsed-indicator button through the proposed slot, with the existing default behavior preserved when no custom content is supplied.

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