Remove AjaxLoadingSpinner and CreateLabelDropdown from global namespace

What does this MR do?

Remove AjaxLoadingSpinner and CreateLabelDropdown from global namespace

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

#38860 (closed)