Blender Git Loki

Depsgraph: Avoid relations build time scene datablock expansion

Quite straightforward implementation, allows us to remove all the cherry-picking
update of specified scene/view layer/collection fields. Makes it possible to use
generic function to update scene.

The tricky part is that we need to know view layer pointer before the whole
evaluation starts. So we actually expand scene at initialization of evaluation.
context. This is still a bit of an exceptional case, but at least we still avoid
dangerous cherry-picking update.