The `connect_sockets()` node util function is used to connect sockets
even when inside node groups, when only a "virtual socket" is
available. It takes care of creating the interface in the group, so
that a socket is available in the Input or Output node.
This feature was broken after the change of API, replacing
`tree.inputs` and `tree.outputs` with a unified `tree.interface`.
This commit updates the util to account for this change.
Fixes an exception in the Node Wrangler add-on, when connecting a
socket of a type not yet available in an Input or Output node.
More info here:
https://wiki.blender.org/wiki/Reference/Release_Notes/4.0/Python_API#Node_Groups
Damien Picard