MDL-68353 message: enclose privacy settings within a fieldset

message/templates/message_drawer_view_settings_body_content.mustache

@@ -39,6 +39,8 @@
     <h3 class="h6 font-weight-bold">{{#str}} privacy, message {{/str}}</h3>
     <p>{{#str}} privacy_desc, message {{/str}}</p>
     <div data-preference="blocknoncontacts" class="mb-3">
+        <fieldset>
+            <legend class="sr-only">{{#str}} contactableprivacy, message {{/str}}</legend>
             {{#privacy}}
                 <div class="custom-control custom-radio mb-2">
                     <input
@@ -53,6 +55,7 @@
                     </label>
                 </div>
             {{/privacy}}
+        </fieldset>
     </div>
 
     <div class="hidden" data-region="notification-preference-container">

message/templates/message_index.mustache

@@ -15,7 +15,7 @@
     along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 }}
 {{!
-    @template core_message/message_drawer
+    @template core_message/message_index
 
     This template will render the message drawer.