[Carousel] deeplink to active item

## Feature Request

Tabs has the ability to set the default panel. Carousel does not.
We have a use case where setting the default panel is desirable.

**Describe the solution you'd like**
Since Carousel uses the same panel picker that Tab, add the same functionality in the dialog box allowing a default panel to be set.

**Are there alternatives?**
No alternatives known at this time

Start by comparing the Carousel and Tabs panel-picker dialog implementations, since the issue says they share the same panel picker and Tabs already supports a default panel. Trace how the Tabs dialog exposes and applies that setting, then confirm the Carousel dialog supports the equivalent behavior.

Written by the indexing model from the issue text.