Summary:
ContainmentActions had some old windows code was dropped as that's
clearly unused.

logout and leave actions now enable/disable at runtime, so in future can
respond to config changes when that's added to libkworkspace.

DataEngines and the krunner code should have no visible changes

Test Plan:
Left from the desktop and from krunner
Changed the default action in ksmserver's kcm
Confirmed that changes the default leave action changed

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: broulik, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D21764