use arg size for parallel iteration

we already know the length of the args, so we can use that length for
parallel iteration and cut down on allocations for `url_for` calls.

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -215,7 +215,7 @@ def optimize_routes_generation?(t)
 
             def parameterize_args(args)
               params = {}
-              @required_parts.zip(args.map(&:to_param)) { |k,v| params[k] = v }
+              @arg_size.times { |i| params[@required_parts[i]] = args[i].to_param }
               params
             end