Add simple identifier to public SSH keys

What does this MR do?

Adds a simple identifier of user_name + hostname to public SSH keys

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

Why was this MR needed?

To help people identify keys when they export them

What are the relevant issue numbers?

#18866 (closed)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• [ x] CHANGELOG entry added
• [ -] Documentation created/updated
• [ -] API support added
• Tests
  • [ x] Added for this feature/bug
  • [ x] All builds are passing
• [ x] Conform by the style guides
• [ x] Branch has no merge conflicts with master (if you do - rebase it please)
• [ x] Squashed related commits together Closes #18866 (closed)