Summary:
This change adds support for marking the OnScreenMessage as it should
skip close animation. The screenshot effect is adjusted to use the
on screen message instead of the custom effect frame.

Test Plan: Message window is not captured when taking screenshot

Reviewers: #kwin, #plasma_on_wayland

Subscribers: plasma-devel, kwin

Tags: #plasma_on_wayland, #kwin

Differential Revision: https://phabricator.kde.org/D4091