Inconsistent lack of casing for highway=living_street polygons

[imagico]

Noticed that we have not been drawing a casing around highway=living_street polygons since at least #1736 - which is kind of inconsistent with the rendering of linear highway=living_street and the way we render highway=pedestrian polygons.

[jeisenbe]

Also see #3891 - currently the parking area fill color is almost identical to the living_street color, since #2934 changed it from yellow. The lack of casing is one of the only distictives, though it is confusing. We should address #3891 at he same time or before this issue is fixed.