Make smoothstep and step nodes more user friendly

[QbieShay]

Describe the project you are working on

VFX

Describe the problem or limitation you are having in your project

When creating a smoothstep and step node, visual shader auto connects to the first port, which is "edge", which is almost never the case in the flow of development of VS: normally you drag out the pin from the value first and add the edges later. At least for me, I haven't dragged the edge first so far, it's always been the value.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

There's two options to solve this:

1. change the order of parameters in the shader nodes (compat-breaking)
2. give nodes an option to specify the default port for connection (not compat breaking)

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

add a get_default_port overrideable function

If this enhancement will not be used often, can it be worked around with a few lines of script?

no

Is there a reason why this should be core and not an add-on in the asset library?

yes