Port "Improve "Share with group lock" feature for subgroups" to EE

What does this MR do?

Port https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13944 to EE.

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

The docs used to say that "Share with group lock" is only in EE. But it was in CE for a long time so we are leaving it in and updating the docs to not say it's only in EE.

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• 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?

CE issue https://gitlab.com/gitlab-org/gitlab-ce/issues/30550