Changed build header username area to use the full name with the username as the tooltip

What does this MR do?

Changes build header username to use the full name with the username as the tooltip.

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

Why was this MR needed?

UI consistency

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• 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 you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Contributes to #21832 (closed)