Node variadic inputs to represent T as T[]

A node which takes a Vec should be able to expose itself as a variadic input, which looks like this:

| 100% Zoom | 200% Zoom |
|--------|--------|
|  |  |

*(7x14 rectangle with 2px rounding)*

Multiple wires can enter this. The order of the wires entering the variadic input does matter, and it laid out from top to bottom. The node receives these as a Vec of T and otherwise acts normally.

The node macro can define whether a data type, that's a Vec, is shown as variadic or regular. We should also consider whether we support the Table data type, where multiple wires become multiple table rows.

Start by tracing the node macro's handling of Vec inputs and the variadic-input node-graph behavior described in this issue. Confirm how wire order and top-to-bottom layout should be represented, then define completion around variadic Vec inputs working normally; Table support remains an open design question.

Scritto dal modello di indicizzazione a partire dal testo della issue.