Add RL optimization into urban designer level

[xpyxpyx]

Currently, there is no loop to perform different urban design actions for the city planner level. Down the line, an an RL loop to perform optimal actions is required.

[xpyxpyx]

The first urban designer action is to control the speed limits, which requires a method to generate patch files for the net.xml as described in SUMO docs. The speed limit action space is 30, 50, 80, 100 and 120 km/h, depending on the road's speed limit. Should other speed limits be featured in the network, they should be matched to the nearest limit available.