Fix issues on groups group trees

What does this MR do?

Recover from an error related to preloading parents when filtering (https://gitlab.com/gitlab-org/gitlab-ce/issues/40785): Preloading is still required, but if for some reason the parent wasn't preloaded, we fall back causing an extra query and report the error in sentry with more detail.

This also makes the projects shared with a group available on the page again. It partially reverts https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16584 for that.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

• First step in https://gitlab.com/gitlab-org/gitlab-ce/issues/40785
• Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/42407