Add service to block Posthog

Postponed on finishing the Posthog module.

Cookieless tracking example: https://git.drupalcode.org/project/klaro/-/blob/3.x/config/install/klaro...

See ✨ Add service to block eTracker Active for similar implementation

posthog_cookies is now ready inside the Posthog module. Perhaps we should just add posthog_klaro submodule there.