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::FileWidgets users can use it.
The file's contents are copied from Dolphin and updated, 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