Ensure uploads are not cached without revalidation

What does this MR do?

changes Caching-Headers on /uploads controller to disable local agent caching without revalidation by adding must_revalidate and max_age=0.

Why was this MR needed?

When uploading Avatar sometimes the heuristics of local agent set the cached expiry so long that new avatar wasn't updated on page refresh. This MR ensures that Avatar and all other uploaded images will not Display without revalidating the cache.

Does this MR meet the acceptance criteria?

• Changelog entry added
• 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 #27936 (closed)