Add support for NorthStar engine

[schaefi]

Description

NorthStar is like podman a container engine. It uses a different format for the containers and also implements different mechanics for starting and managing containers. In order to support users who prefer northstar over podman we would like to add support for this engine.

Acceptance Criteria

• Implementation of northstar-pilot exists and is able to startup a NorthStar compatible container, runs an application inside and works comparable to the existing podman engine implementation
• Implementation of app registration exists as part of flake-ctl