The Pass struct is now a Node and the passes are moved from the Film
class to the Scene class.
The Pass Node only has `type` and `name` as sockets as those seem to be
the only properties settable by exporters (other properties are implicit
and depend on the pass type).
This is part of T79131.
Reviewed By: brecht
Differential Revision: https://developer.blender.org/D8591
1da0685076