moving duckiebots controller updated to handle other moving bots

[mostafaelaraby]

If we try to use a map with more than one moving duckiebots they might hit each other on corners if one is slowing and the other is coming faster and this issue would throw an exception closing the gym.
So the proposed fix is to use the proximity function to check if there's any other duckiebot within safety range and slow down accordingly.
@bhairavmehta95