Glow effect does not respect the depth order

Rotate camera: https://playground.babylonjs.com/#QCJQR4#75

Looks like meshes are not sorted by depth before rendering to glow effect.

I tried to sort meshes manually in scene hierarchy, this does not help. However this method work with rendering to framebuffer. But does not work with rendering to effect.

And I tried to use scene.setRenderingOrder(). This also work with rendering to framebuffer but does not work with rendering to effect.

Transparency is important: meshes sometimes should be partially masked.

cc @sebavan

Glow and highlights layer do not support transparency or in a pretty limited way :frowning: Let me see if I can find smthg to improve this