Enable correct spawning at upstream lanes

In trafficAreaAction, spawning was not happening correctly when vehicles are coming at the upstream, this PR address by creating the leading entities based on their direction. If the lane is from the Opposite flow direction (Upstream) , the entry distance should be the end of the road and spawn distance should be relative to the end of the road. That happens because the 'end' in the upstream point of view is the starting point of the spawned vehicles.