Nested groups path restrictions pt. 1

What does this MR do?

Does not allow nested group path to be one of wildcard project routes like tree, blob, commits etc. This is pt. 1 includes restrictions that does not affect existing projects.

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

no

Why was this MR needed?

To prevent routing mismatch and make it possible to differentiate git traffic and web traffic.

Does this MR meet the acceptance criteria?

• Changelog entry 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?

https://gitlab.com/gitlab-org/gitlab-ce/issues/2772 and https://gitlab.com/gitlab-org/gitlab-ce/issues/28125#note_24871361