Correctly escape UTF-8 path elements for uploads

What does this MR do?

Fixes linking to uploads with UTF-8 in the filename

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

Why was this MR needed?

regression on GitLab.com . Without this, some existing links can't be rendered.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #42159 (closed)