Fix EWMH non-compliance for NET::{OnScreenDisplay,CriticalNotification}

Summary:
The EWMH specification for _NET_WM_WINDOW_TYPE states:

The Client SHOULD specify window types in order of preference
(the first being most preferable) but MUST include at least one of
the basic window type atoms from the list below. This is to allow
for extension of the list of types whilst providing default behavior
for Window Managers that do not recognize the extensions.

KDE currently does not do this for its extended window types due to
what appears to be a copy-paste error 5 years ago, and so is not
EWMH compliant. This also causes focus stealing issues with i3 that
lack a workaround: https://github.com/i3/i3/issues/3937

Reviewers: KWin, davidedmundson

Reviewed By: KWin, davidedmundson

Subscribers: ngraham, davidedmundson, broulik, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D27356