[autotests] Test window open/close animations

Summary:
The idea behind this autotest is to verify that different window
open/close animation effects behave similarly.

Currently, we just check whether Fade/Glide/Scale effect tries to animate
the appearing or the disappearing of toplevels. In the future, the
autotest will be extended to verify that there are no conflicts between
those three effects and the Login/Logout effect, etc.

Test Plan: Ran the test, found a bug in the Fade effect, fixed it.

Reviewers: #kwin, graesslin

Reviewed By: #kwin, graesslin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D17526