Summary:
So far both Workspace and Toplevel emitted signals for every property
notify event on the root window and the respective Toplevel windows. The
signals were only used in EffectsHandlerImpl to forward to the effect
system in case the property which changed is registered by an effect.

This change introduces a dedicated event filter for this which is only
created in EffectsHandlerImpl in case an X11 connection is available. It
supports a restart of the X11 system.

The signals used so far are removed from Workspace and Toplevel.

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D7853