Add a custom WaylandSurfaceNode with its own materials

Add a custom WaylandSurfaceNode with its own materials

With the previous WaylandSurfaceNode based on QSGSimpleTextureNode,
QSGTexture's created from SHM buffers would always have and use their
alpha channels, despite the useTextureAlpha flag being set to false. Now
when the useTextureAlpha flag is set to false, we use a material that
ignores the textures alpha channel.

Change-Id: I9cc33939f37856495f8885357f49de5ffdd81d1f
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>