Show Advisory Speed Limit by default on link presets in Canada, U.S.

Canada and the United States generally post only an advisory speed limit and avoid posting a legal speed limit on highway ramps. Other countries differ. This change splits the maxspeed field into two as a workaround for the inability to limit the default inclusion of a field to a particular location set.

interim/source_strings.yaml

@@ -1496,6 +1496,18 @@ en:
         # maxspeed/advisory field placeholder
         placeholder: '40, 50, 60...'
         terms: '[translate with synonyms or related terms for ''Advisory Speed Limit'', separated by commas]'
+      maxspeed/advisory_mutcd:
+        # 'maxspeed:advisory=*'
+        label: Advisory Speed Limit
+        # maxspeed/advisory_mutcd field placeholder
+        placeholder: '40, 50, 60...'
+        terms: '[translate with synonyms or related terms for ''Advisory Speed Limit'', separated by commas]'
+      maxspeed_mutcd:
+        # maxspeed=*
+        label: Speed Limit
+        # maxspeed_mutcd field placeholder
+        placeholder: '40, 50, 60...'
+        terms: '[translate with synonyms or related terms for ''Speed Limit'', separated by commas]'
       maxstay:
         # maxstay=*
         label: Max Stay