Convert radios on set-service-setting.html

Uses the ServiceOnOffSettingForm.enabled.

Effects the following routes:
- /services/<service_id>/service-settings/switch-live
- /services/<service_id>/service-settings/switch-count-as-live
- /services/<service_id>/service-settings/permissions/<permission>
- /services/<service_id>/service-settings/permissions/broadcast

Includes changes to make the GOVUK radios
component render the h1 in the page. This is done
so the legend doesn't just duplicate the h1 and
is recommended in the design system guidance for
the radios component for pages that just ask you
for one piece of information.

https://design-system.service.gov.uk/components/radios/#how-it-works

app/templates/views/service-settings/set-service-setting.html

@@ -1,8 +1,7 @@
 {% extends "withnav_template.html" %}
-{% from "components/radios.html" import radios %}
-{% from "components/page-header.html" import page_header %}
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/form.html" import form_wrapper %}
+{% from "components/back-link/macro.njk" import govukBackLink %}
 
 {% block service_page_title %}
   {{ title }}
@@ -12,12 +11,20 @@
 
   <div class="govuk-grid-row">
     <div class="govuk-grid-column-five-sixths">
-      {{ page_header(
-        title,
-        back_link=url_for('.service_settings', service_id=current_service.id)
-      ) }}
+      {{ govukBackLink({
+        "text": "Back",
+        "href": url_for('.service_settings', service_id=current_service.id)
+      }) }}
       {% call form_wrapper() %}
-        {{ radios(form.enabled, hide_legend=True) }}
+        {{ form.enabled(param_extensions={
+          "fieldset": {
+            "classes": "govuk-!-margin-top-3",
+            "legend": {
+              "isPageHeading": True,
+              "classes": "govuk-fieldset__legend--l"
+            }
+          }
+        }) }}
         {{ page_footer('Save') }}
       {% endcall %}
     </div>