Fix misleading “specified upload does not exist”

Why it matters

This fix addresses a race condition in multipart uploads where the original exception was lost, causing an incorrect and misleading error message. It improves error reporting accuracy, helping users diagnose upload issues more effectively.

How to use it

This fix is applied internally within ClickHouse and does not require any user action to enable. Users will automatically benefit from improved error messages when performing multipart uploads after upgrading to the version containing this fix.