This changes the drawing of the zone nodes to align corresponding input
and output sockets. The resulting nodes are smaller and it's easier to see
how data is passed through them.
Drawing aligned sockets is already technically supported for quite a while
already, but we haven't used it so far. Using them for zone nodes seems to
provide benefits only. How we use aligned sockets in other nodes still has
to be discussed more.
This patch only changes run-time data. It doesn't affect what is written to
.blend files.
In the node declaration, aligned sockets are created by tagging a socket
so that it is aligned with the previous socket. This is a bit different from
what we had before where a single socket declaration would be used for
an input and output socket. I think the approach used here works better,
especially in a potential future scenario where the input and output socket
has a different type.
Pull Request: https://projects.blender.org/blender/blender/pulls/118335