Make use of new RoomMember item from libquotient

Depends on https://github.com/quotient-im/libQuotient/pull/695

Currently basic just to show a working implementation using RoomMember. Currently only the room event and search models are moved over. Will change everything else over once the dependent pr is complete.

src/models/searchmodel.cpp

@@ -85,7 +85,7 @@ QVariant SearchModel::data(const QModelIndex &index, int role) const
     case ShowAuthorRole:
         return true;
     case AuthorRole:
-        return eventHandler.getAuthor();
+        return QVariant::fromValue(eventHandler.getAuthor());
     case ShowSectionRole:
         if (row == 0) {
             return true;