[Sync EN] Add documentation for 6 new pcntl functions (PHP 8.4)

PR: `https://github.com/php/doc-en/pull/5350` (2026-06-07)

**Новые файлы EN (ещё не переведены)**
- `reference/pcntl/functions/pcntl-forkx.xml`
- `reference/pcntl/functions/pcntl-getcpu.xml`
- `reference/pcntl/functions/pcntl-getqos-class.xml`
- `reference/pcntl/functions/pcntl-setns.xml`
- `reference/pcntl/functions/pcntl-setqos-class.xml`
- `reference/pcntl/functions/pcntl-wifcontinued.xml`

