Fix error messages on project settings page

What does this MR do?

This MR displays error messages always on top of the project settings page. It also displays the error message if the request is not an AJAX request (happens when the user selects an avatar image).

Why was this MR needed?

To always show an error message (for AJAX and normal requests).

Does this MR meet the acceptance criteria?

• Changelog entry 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?

Closes #24319 (moved)