Add group webhooks to registration features

What does this MR do and why?

We want to add Group webhooks to features available to users who have service ping data sharing enabled.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Testing previous behavior:
   • Make sure you're on a Premium/Ultimate plan GitLab GDK instance
   • Select some group
   • Select Settings -> Webhooks in Group sidebar
   • Create new webhook for Comments. You can use https://webhook.site/ for testing purposes.
   • Add comment to any issue that is related to this group.
   • Verify used webhook callback url log (it must be called).
2. When registration features are enabled:
   • Make sure you're on a free plan GitLab GDK instance (for example, remove current license or stub #current to return nil)
   • Make sure you have the Registration Features checkbox enabled (Admin -> Settings -> Metrics and profiling -> Usage statistics -> Enable Service Ping & Enable Registration Features)
   • Follow steps from 1. to verify it.
3. When registration features are disabled:
   • Make sure you're on a free plan GitLab GDK instance
   • Make sure you have the registration features checkbox disabled (Admin -> Settings -> Metrics and profiling -> Usage statistics -> Enable Registration Features)
   • Select some group
   • Select Settings -> Webhooks in Group sidebar
   • Group webhooks feature should be disabled
4. Make sure that the new text appears on the docs page:
   • run gdk restart gitlab-docs
   • go to <local_gitlab_docs_host>/ee/user/admin_area/settings/usage_statistics.html#registration-features-program and make sure the new section is on the page and the link works

Updated doc	Link page

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #422270 (closed)