Summary:
A new virtual method createOpenGLSafePoint is added to Platform.
This is invoked through the Compositor with a PreInit and a PostInit
argument pre and post creating the SceneOpenGL.

The Platform plugin can implement this and use it for detecting whether
creating the OpenGL compositor on this platform crashed in the past.
Thus it's the base for the openGLIsBroken platform check.

The x11 standalone plugin is the first to implement this functionality
using the previous code which was designed for X11.

This also means that a crash of the OpenGL compositor during init on
Wayland won't result in OpenGL being disabled.

Reviewers: #plasma

Subscribers: plasma-devel

Projects: #plasma

Differential Revision: https://phabricator.kde.org/D1582