Group IO node should have converse passthrough sockets

Group IO nodes should have a matching set of IO sockets on the other side of the node.
This would allow for quick value tweaking/testing while editing the group (without having to detach/reattach anything), as well as making it so that ungrouping a group doesn't result in any unconnected input/output sockets just entirely vanishing.
These sockets are always identical to their converse ones, and when outside of a group always "pass through" whatever values are put into them, effectively making them reroute nodes that can also have default values.

Rough photoshops of what I mean:

Normal node format

Mildly cursed looking but also probably more elegant "double-ended" format.