Add depends option to set edges without future inputs

[liamgriffiths]

When you would like to control the ordering of nodes in the graph, but do not want to connect nodes via future input args we're implementing the depends option on Node to specify what nodes a node depends on.

What this looks like:

      const a = new FooNode({ a: 123 }, { id: "a" });
      const b = new FooNode({ b: 456 }, { id: "b", depends: [a] });
      const c = new FooNode({ c: 789 }, { id: "c", depends: [a, b] });

When we serialize the graph we'll set the edges key in the API JSON that we'll use on the server when scheduling nodes.