Hide early parking when no area, show parking areas earlier

[nvkelso]

            hide-until-z18-no-area:
                filter:
                    $zoom: { max: 18 }
                    area: false
                    kind: [bench, parking, waste_basket]
                draw:
                    mapzen_icon_library:
                        visible: false

[nvkelso]

Bench and waste_basket are already min_zoom 18.

Parking should really be area classes, with zoom 18 default if no area:

• node, zoom 18: https://www.openstreetmap.org/node/1706619902#map=19/37.77619/-122.44515
• way small, zoom 17: https://www.openstreetmap.org/way/506510951#map=17/37.73077/-122.48156
• way medium, zoom 16: https://www.openstreetmap.org/way/162093420#map=16/37.7286/-122.4760
• way huge, zoom 15: https://www.openstreetmap.org/way/32928608#map=15/37.7293/-122.4853

[nvkelso]

(This other PR is bike parking, not really related to https://github.com/tilezen/vector-datasource/pull/1727/files.

[nvkelso]

QA verified.