[Feature Request] Add raycast or change the obstacle into circle

[LianhaoYin]

In vector observation, there is no direct distance measurement of obstacles.

option1: Add raycast but it will slow down the speed
option2: change the square obstacles to circles and one can easily calculate the distance to the obstacles.

[mlech26l]

Let's disable the obstacles/maps for now (in the scenarios, set the map to "empty")

I will think about how to solve this.

[mlech26l]

Let's define the state-vector obs scenarios only with the "empty" map (i.e., maps can only be used with RGB obs)