Dolphin: port to CommandLauncherJob

Summary: git master already requires 5.69 anyway, due to KBookmarkMenu API change

Test Plan: Builds, Tools / Compare Files works.

Reviewers: broulik, elvisangelaccio, meven

Reviewed By: elvisangelaccio, meven

Subscribers: kfm-devel

Tags: Dolphin

Differential Revision: https://phabricator.kde.org/D28589