CE backport of E2E Test wiki SSH push to Geo primary node

What does this MR do?

Backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/16351

• Adds qa selectors to wiki show page and ssh keys page (and updated the related page objects) for more specific RSpec assertions
• Add method to wiki_push resource to find ssh_uri

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content