autocomplete [nfc]: Group comparison/sorting methods together

These two methods were in between compareByRecency and compareByDms,
which are closely-related siblings to each other.  So move them
outside that group.

Author: gnprice

lib/model/autocomplete.dart

@@ -311,6 +311,19 @@ class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery,
   final Narrow narrow;
   final List<User> sortedUsers;
 
+  @override
+  Iterable<User> getSortedItemsToTest() {
+    return sortedUsers;
+  }
+
+  @override
+  MentionAutocompleteResult? testItem(MentionAutocompleteQuery query, User item) {
+    if (query.testUser(item, store.autocompleteViewManager.autocompleteDataCache)) {
+      return UserMentionAutocompleteResult(userId: item.userId);
+    }
+    return null;
+  }
+
   static List<User> _usersByRelevance({
     required PerAccountStore store,
     required Narrow narrow,
@@ -417,19 +430,6 @@ class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery,
         streamId: streamId, senderId: userB.userId));
   }
 
-  @override
-  Iterable<User> getSortedItemsToTest() {
-    return sortedUsers;
-  }
-
-  @override
-  MentionAutocompleteResult? testItem(MentionAutocompleteQuery query, User item) {
-    if (query.testUser(item, store.autocompleteViewManager.autocompleteDataCache)) {
-      return UserMentionAutocompleteResult(userId: item.userId);
-    }
-    return null;
-  }
-
   /// Determines which of the two users is more recent in DM conversations.
   ///
   /// Returns a negative number if [userA] is more recent than [userB],