Resolve "Promote webhooks"

What does this MR do?

It promotes Group Hooks. It enables the Webhook navigation point if we are showing a promotion and it will show the promotion then on that page. The basic rules of how and what to show for promotions were already established & extensively reviewed here : gitlab-org/gitlab-ee!2540 This MR is following and applying the same patterns here.

Are there points in the code the reviewer needs to double check?

There is also one small change to the contribution analytics promotion to align the design there properly

Why was this MR needed?

To promote our awesome EE features to all the people who don't have them yet.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #2947 (closed)