Improve URL checks to reduce false-negatives

This commit improves the URL health checking mechanism to reduce false
negatives.

- Treat all 2XX status codes as successful, addressing issues with codes
  like `204`.
- Exclude URLs within Markdown inline code blocks.
- Send the Host header for improved handling of webpages behind proxies.
- Improve formatting and context for output messages.
- Fix the defaulting options for redirects and cookie handling.
- Add URL exclusion support for non-responsive URLs.
- Update the user agent pool to modern browsers and platforms.
- Improve CI/CD workflow to respond to modifications in the
  `test/checks/external-urls` directory, offering immediate feedback on
  potential impacts to the external URL test.
- Add support for randomizing TLS fingerprint to mimic various clients
  better, improving the effectiveness of checks. However, this is not
  fully supported by Node.js's HTTP client; see nodejs/undici#1983 for
  more details.
- Use `AbortSignal` instead of `AbortController` as more modern and
  simpler way to handle timeouts.

tests/checks/desktop-runtime-errors/check-desktop-runtime-errors/utils/run-command.ts

@@ -1,5 +1,6 @@
-import { exec, type ExecOptions, type ExecException } from 'node:child_process';
-import { indentText } from './text';
+import { exec } from 'child_process';
+import { indentText } from '@tests/shared/Text';
+import type { ExecOptions, ExecException } from 'child_process';
 
 const TIMEOUT_IN_SECONDS = 180;
 const MAX_OUTPUT_BUFFER_SIZE = 1024 * 1024; // 1 MB