Reintroduce testing zephyr application on real hardware (U585 board)

[kr-t]

Flashing hardware and testing it was temporary removed. Reintroduce the tests, follow the repositories common test structure; if necessary, provide documentation. UNH-IOL can provide in lab help, if necessary.

[kr-t]

@PatrickRobbIOL this can be used as the main task from yesterday's discussion.