Feature request

Feature description

The collision_monitor polygons are dynamic, by subscribing to a topic on which the list of polygon's points are published.
The circle polygon could be dynamic as well.

Implementation considerations

In order to keep a design similar to the other polygons, the circle polygon could be updated by subscribing to a topic on which the radius would be published.
The topic can be defined by using the same parameter than for the other polygons: <polygon_name>.polygon_sub_topic (the subscription type would be defined by the polygon type).
In order to not break the current usage, if no topic is defined as a parameter, the parameter <polygon_name>.radius will be used.
I can open a PR with an implementation of this solution.