EE port 35659 Rename Pipelines tab to CI / CD in new navigation

What does this MR do?

EE port of ce#35659 Renames pipelines to CI / CD in new navigation

CE MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13241

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?