[bug] when scale is changed, the walls will not align with the map

[clay-arras]

description: when the SCALE global variable in continuous_env/robot_obstacles.py is increased to a larger number (i.e. 30), the walls will not align with the edges of the map, causing gaps and unnatural environment generation

criteria:

• revamp the obstacle rendering such that no matter what the scale is, the rendering will always fill the whole map
• the rendered area should match the intended “playable” area of the map in all dimensions, regardless of the chosen SCALE