The goal here is to simplify working with the common pattern where a Menu Switch
node is followed by an Index Switch node. This is achieved by detecting this
pattern and drawing the item names from the menu switch node in the index switch
node.
This slightly refactors the custom socket drawing callback to make it easier for
it indirectly call the default drawing function.
Pull Request: https://projects.blender.org/blender/blender/pulls/145710
1fd6d9263c