This moves most of the code to deal with syncable nodes (such as
Combine/Separate Bundle) to the nodes module. Over time it might be possible to
decentralize it more.
This also changes the caching mechanism from storing a flag on the node to
storing a map on the node editor runtime data. This simplifies the code quite
significantly and also removes the need to store any of this data in DNA.
The node tree update code now always clears this cache because before it was
missing many cases, e.g. when creating links that would connect a Combine to a
Separate Bundle node.
Pull Request: https://projects.blender.org/blender/blender/pulls/143661
1260e90b4c