Blender Git Loki

Proper implementation of compositor support for Draw Manager

We need to move the render result logic outside the render engine code.

It makes no sense for Eevee/Clay/... to have to re-implement the render resilt
creation logic. Beside the original implementation really got it wrong, by
ignoring the different render layers needed for the final render.

Finally, there is no need to re-create the logic for views. So this was also
fixed.

Note 1: This will break still if the depsgraph of the needed view layers is not
updated / created. We need to address this separately. For now if users want
to test this, just show each view layer in the viewport at least once.

Note 2: We are still getting depsgraph from scene and creating if needed.
`BKE_scene_get_depsgraph(scene, view_layer, true);` according to Sergey we need
to move the render depsgraph for the Render struct instead. I will do it
separately as well.