Consistent focus outline styles across core and plugins

Description

The focus outline styles currently deviate in a few places. They should be streamlined, so only two focus outline styles are used:

• Elements that are being displayed directly over the map (e.g. PolarIconButton)
• Elements that are being used in a context that include a background

Current behavior

Outlines are sometimes styled by KERN, sometimes they use the native outline styles and in the case of the PolarIconButton we use completely different approach.

Expected behavior

Any element that is being displayed directly on the map should use the focus outline styling of the PolarIconButton.
Any other element should use the KERN default focus outline.

outline: 4px solid var(--kern-color-action-focus-default-contextual, #454B6B);
outline-offset: 2px;

Out of scope

Only the focus style should be changed, no logic.