Refactoring the hidding/showing animation use within KFilePlacesView

Summary:
Depends on D8367
Depends on D8450

Test Plan: manual testing on the context menu

Reviewers: ervin, renatoo, mlaurent, ngraham

Reviewed By: ervin

Subscribers: Frameworks

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D9015