add icons to kerb fields, tweak label, drop from specialized presets

specialized presets should be switched using the preset selector, no need to duplicate that as a combo box. this effectively reverts https://github.com/openstreetmap/iD/issues/6360

(re icons, see also https://github.com/openstreetmap/id-tagging-schema/pull/1077#issuecomment-1966247784)

also remove duplicates of translatable strings

data/presets/barrier/kerb/flush.json

@@ -1,9 +1,5 @@
 {
     "icon": "temaki-kerb-flush",
-    "fields": [
-        "kerb/kerb_barrier",
-        "{barrier/kerb}"
-    ],
     "geometry": [
         "vertex",
         "line"

data/presets/barrier/kerb/lowered.json

@@ -1,7 +1,6 @@
 {
     "icon": "temaki-kerb-lowered",
     "fields": [
-        "kerb/kerb_barrier",
         "{barrier/kerb}",
         "kerb/height"
     ],

data/presets/barrier/kerb/raised.json

@@ -1,7 +1,6 @@
 {
     "icon": "temaki-kerb-raised",
     "fields": [
-        "kerb/kerb_barrier",
         "{barrier/kerb}",
         "kerb/height"
     ],

data/presets/barrier/kerb/rolled.json

@@ -1,7 +1,6 @@
 {
     "icon": "temaki-kerb-rolled",
     "fields": [
-        "kerb/kerb_barrier",
         "{barrier/kerb}",
         "kerb/height"
     ],