After the recent introduction of node panels, the utility that
allowed scripters to connect sockets to or from a virtual socket was
broken. This happens when creating an interface before connecting
sockets. Sockets can have a subtype, while interfaces cannot.
For instance, the `NodeSocketFloatFactor` type cannot be used
directly, it has to be converted to `NodeSocketFloat`.
This commit chooses an appropriate type for the new interface before
creating it, based on the socket's `type` property.
Pull Request: https://projects.blender.org/blender/blender/pulls/113630
fa5bb53f5c