Handle post instantiation graph modification

[CJ-Wright]

There are three main methods for modifying the graph after the nodes are instantiated, move_to_first which changes the upstream ordering, .connect which adds nodes to the upstreams, and .disconnect which is the inverse of .connect. .disconnect is not used frequently so we'll neglect it here.

To identify .connect we can examine the node args (which contain which nodes were subscribed to at init time) and the .upstreams attribute, which holds the current upstreams. Whatever nodes are in .upstreams which are not in args were connected in. This is important as we need to match the .connect syntax and usage for true pipeline recreation, since .connect can be used to create cyclic graphs, which are currently forbidden in the pipeline recreation step (since we do a topo sort and need to have higher nodes present in order to subscribe to them).

To identify move_to_first we need to compare the ordering of the args and the .upstreams. Here we need to match the .upstreams order wit the final pipeline.