KIO didn't actually have its own rename dialog, which is necessary to implement the requested rename-from-the-file-dialog feature (189482). This patch upstreams Dolphin's dialog so all KIO users can use it.
The file's contents are copied verbatim from Dolphin, but the name is changed from `RenameDialog` to `RenameFileDialog` because `RenameDialog` already exists in KIO (and is actually an //overwrite// dialog, but we can't rename it until KF6).
CCBUG: 189482