Upstream Dolphin's file rename dialog

Summary:
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

Test Plan:
Apply D17596 or D17597 and initiate a rename operation for one or more files. See that it works as expected.

Tests still pass.

Reviewers: Frameworks, Dolphin, broulik, ngraham, dfaure, elvisangelaccio

Reviewed By: Dolphin, ngraham, dfaure, elvisangelaccio

Subscribers: elvisangelaccio, lydia, dfaure, sitter, mitchell, emmanuelp, ltoscano, bruns, meven, dhaumann, pino, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D17595