Long node graph evaluations hang frontend

[0HyperCube]

Despite all of the weird and hacky things we have to pass node graph evaluations to another 'thread' both browsers I have tested (firefox-dev and msedge) appear to evaluated the node graph on the main thread. This was confirmed both by running an expensive node and using the profiler.

[Keavon]

This is sort of tracked by #1113 although that issue is probably due for an updated description. The latest comments in the thread are more relevant to what's required to finish that implementation.