Investigate why WebCrypto platfrom test don't fail if we modify them for failure

[olegbespalov]

What?

Originally spotted by @McMastS in #4263 (comment)

It seems like the WebCrypto's web platform tests don't fail if we deliberately modify them for failure.

E.g. the script like

import { crypto } from "k6/experimental/webcrypto";

export default async function () {
  const key = await crypto.subtle.generateKey(
    {
      name: "Ed25519"
    },
    true,
    ["sign", "verify"]
  );

  console.log(JSON.stringify(key));
}

At that state of WebCrypto should fail since Ed25519 isn't supported, but if we uncomment it in internal/js/modules/k6/webcrypto/tests/wpt/WebCryptoAPI/generateKey/successes.js

tests still passed 🤔

We need to figure out, why this happens and apply fix if needed.

Why?

Having a working and reliable tests is essential.