Blender Git Loki

Nodes: Refactor to remove node and socket "new" pointers

These pointers point to the new nodes when duplicating,
and their even used to point to "original" nodes for
"localized" trees. They're just a bad design decision
that make code confusing and buggy.

Instead, node copy functions now optionally add to a map
of old to new socket pointers. The case where the compositor
abused these pointers as "original" pointers are handled
by looking up the string node names.

Differential Revision: https://developer.blender.org/D13518