ci/cd: trigger URL checks more, and limit amount

Fix all URL checks failing in GitHub runner due to:

- Missing Happy Eyeballs in Node.js
  nodejs/undici$1531
  nodejs/node$41625
- Missing IPv6 support in GitHub runners:
  actions/runner$3138
  actions/runner-images$668

Tried (did not work):

1)

```
import dns from 'dns';
dns.setDefaultResultOrder('ipv4first');
```

2) Bumping node to v20.

3) TODO: Try autoSelectFamily

- Or is it due too to many max connections? Test this.
  Mentioned in comment nodejs/node$41625.

Key changes:

- Run URL checks more frequently on every change.
- Introduce environment variable to randomly select and limit URLs
  tested, this way the tests will provide quicker feedback on code
  changes.

Other supporting changes:

- Log more information about test before running the test to enable
  easier troubleshooting.
- Move shuffle function for arrays for reusability and missing tests.

.github/workflows/checks.external-urls.yaml

@@ -1,6 +1,7 @@
 name: checks.external-urls
 
 on:
+  push:
   schedule:
     - cron: '0 0 * * 0' # at 00:00 on every Sunday
 
@@ -20,3 +21,7 @@ jobs:
       -
         name: Test
         run: npm run check:external-urls
+        env:
+          RANDOMIZED_URL_CHECK_LIMIT: "${{ github.event_name == 'push' && '10' || '' }}"
+          # - Scheduled checks has no limits, ensuring thorough testing.
+          # - For push events, triggered by code changes, the amount of URLs are limited to provide quick feedback.