Update `NavigationBar` to use the `Chip` component from design system

### Description

There is a new `Chip` component in the design system, which when used as a toggle chip (without checkmarks) behaves exactly the same as our `NavigationBar`. I think we should switch over to using that instead of implementing our own since this will get automatic styling updates along with the design system. The existing component has had to be updated several times to keep up with changes in for example focus styling.

https://digdir.github.io/designsystem/?path=/story/kjernekomponenter-chip--toggle-chip

### Additional Information

_No response_

Start by locating the existing NavigationBar component and its tests, then compare its toggle behavior with the design system's Chip toggle-chip example. Replace the custom implementation with Chip while preserving NavigationBar behavior, and verify the existing tests and focus-state behavior pass.

Written by the indexing model from the issue text.