Runner for executing commands on remote device

Summary: Add a runner that allows executing commands on a connected device. It enables a more keyboard-centric workflow than running the commands from the plasmoid.

Test Plan: Connect desktop device. Add some commands there. restart krunner, open it, start typing command or device name. Select entry to execute command. Check for success.

Reviewers: KDE Connect, Plasma, broulik, davidedmundson, apol

Reviewed By: KDE Connect, apol

Subscribers: apol, ngraham, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D14604