Adjust Task Manager to libtaskmanager API changes for Wayland virtual desktop support
Summary:
Depends on D13745.
This code is largely untested and subject to change.
Reviewers: mart, davidedmundson
Reviewed By: davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Maniphest Tasks: T4457
Differential Revision: https://phabricator.kde.org/D13746