Set Material node should work in a similar way to the group node

I propose that we should be able to interact with the Set Material node in the same way we do with a group node. This could be implemented in two ways:

• The first is to be able to open the shader editor by pressing TAB while a set material node is selected and returning to the geometry node editor by pressing TAB again, just like in a group node. This should be easy to implement and would not require structural changes to the way the shader editor works.

• The second would be for materials to have group inputs and outputs, just like group nodes, that would show on the Set Material node. This is harder to implement, but would allow for a more seamless workflow between shading and geometry nodes and would simplify the current process of transferring information between the two.