Improve poi shop style (#1634)

The main goal is to improve consistency and reduce the number of poi without an icon.

- Remove music from poi cultural, music has only two subclasses music and musical_instrument, both are styled as poi shop
- Remove arts_centre from poi shop, it's already styled as poi cultural
- Remove chocolate icon, chocolate uses confectionery icon (see: https://github.com/openmaptiles/openmaptiles/pull/1628)
- Remove references to ice_cream class from poi shop
- Add missing gallery icon and move it to poi cultural (see: https://wiki.openstreetmap.org/wiki/Tag:tourism%3Dgallery)
- Use the icons alcohol, newsagent, perfumery, trade respectively for wine, kiosk, perfume and wholesale.
- Add a generic fallback icon for shops

layers/poi/style.json

@@ -23,11 +23,29 @@
           ]
         },
         "icon-image": [
-          "match",
-          ["get", "subclass"],
-          "chocolate",
-          "confectionery",
-          ["get", "subclass"]
+          "coalesce",
+          [
+            "image",
+            [
+              "match",
+              ["get", "subclass"],
+              "chocolate",
+              "confectionery",
+              "wine",
+              "alcohol",
+              "kiosk",
+              "newsagent",
+              "perfume",
+              "perfumery",
+              "wholesale",
+              "trade",
+              ["get", "subclass"]
+            ]
+          ],
+          [
+            "image",
+            "shop"
+          ]
         ],
         "text-field": "{name:latin}\n{name:nonlatin}",
         "visibility": "visible",
@@ -41,16 +59,7 @@
         "icon-allow-overlap": true
       },
       "paint": {
-        "text-color": [
-          "match",
-          [
-            "get",
-            "class"
-          ],
-          "ice_cream",
-          "#C77400",
-          "#939"
-        ],
+        "text-color": "#939",
         "icon-opacity": 1,
         "icon-halo-blur": 1,
         "text-halo-blur": 0.5,
@@ -78,7 +87,9 @@
           "subclass",
           "mall",
           "library",
-          "artwork"
+          "artwork",
+          "arts_centre",
+          "gallery"
         ]
       ],
       "order": 155
@@ -124,16 +135,7 @@
         "icon-allow-overlap": true
       },
       "paint": {
-        "text-color": [
-          "match",
-          [
-            "get",
-            "class"
-          ],
-          "ice_cream",
-          "#C77400",
-          "#939"
-        ],
+        "text-color": "#939",
         "icon-opacity": 1,
         "icon-halo-blur": 1,
         "text-halo-blur": 0.5,
@@ -873,7 +875,6 @@
           "class",
           "cinema",
           "library",
-          "music",
           "museum",
           "castle",
           "monument",
@@ -883,9 +884,7 @@
           "!in",
           "subclass",
           "books",
-          "musical_instrument",
-          "art",
-          "gallery"
+          "art"
         ]
       ],
       "order": 168