use Röntgen icon for more presets and field-values

presets:
* Diving Platform
* City Limit Sign
* Turning Loop

fields values:
* `design` field of Power Poles and Power Towers/Portals
* `leaf_type`
* `traffic_calming`
* `volcano:type` and `volcano:status`
* `tower:construction`

data/presets/highway/turning_circle.json

@@ -1,5 +1,5 @@
 {
-    "icon": "maki-circle-stroked",
+    "icon": "maki-circle",
     "geometry": [
         "vertex"
     ],

data/presets/highway/turning_loop.json

@@ -1,5 +1,5 @@
 {
-    "icon": "maki-circle",
+    "icon": "roentgen-turning_loop",
     "geometry": [
         "vertex"
     ],