LibOverride: Preserve viewlayers when creating overrides of collecitons.

Usually, when overriding collections, the linked reference ones are
removed from the ViewLayer, and the overrides replace them.

This change to `layer_collection_sync` code makes it so that in case
there is a free viewlayer hierarchy matching the linked collection, it
gets re-used for the override one, instead of re-creating everything
from scratch.

To achieve this, resync process is split into two steps, first regular
collections are processed, then the override ones. This should ensure
an override does not steal the layers of its reference if the later is
still instantiated in the view layer.

0 files changed, 0 insertions, 0 deletions