post-game task: Adjust defender behavior when striker loses ball

[rmburg]

When the ball is close to the opponent goal and our striker loses sight of it, our defenders on the other side of the goal become searcher and start spinning to look for the ball. This is not ideal, they should ideally keep looking towards the other half of the field.

Idea: we could use a heuristic that delays the transition to searcher based on the distance of the robot to the last known ball position