Use consistent "Suspend" terminology

Summary: We use "Suspend" and "Hibernate" in most places except for KRunner, where we currently use more technical terms that expose the implementation details (suspend to ram vs suspend to disk). Let's be consistent.

Reviewers: #plasma, #vdg, davidedmundson, broulik

Reviewed By: #plasma, davidedmundson, broulik

Subscribers: sudhirkhanger, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D15386