[Bug]: WARN messages can print megabytes of text

[sniku]

k6 version

master

OS

Linux

Docker version and image

No response

Expected Behaviour

WARN messages produced by #1876 should trim the values.

Actual Behaviour

WARN messages can be megabytes long.

Steps to Reproduce the Problem

import http from 'k6/http';
import { Counter } from 'k6/metrics';

let my_counter = Counter("my_counter");

export default function () {
  my_counter.add(http.get('https://test.k6.io').body)
}