Copy the interface socket directly which makes sure that all relevant data is passed on.
The default is still adapted from the current socket value.
There are still places that could be improved that are not covered by this patch yet.
For example creating a group from a Set Position node changes the default Position input.
That could be fixed separately.
I removed one `assert` that did not seem important. It was making sure that an interface
item is only copied within a group, but I don't see a reason for why it should not be possible
to copy an item to a different group.
Pull Request: https://projects.blender.org/blender/blender/pulls/131394
4fd49ae9f3