Allow to fork utility process from a worker thread

[bpasero]

An idea @Tyriar and Electron team discussed is whether we could fork Electron utility processes from a node.js worker to stop the main process from being stopped synchronously until the fork has completed.

If we had a way to fork from a worker thread we can:

• potentially avoid blocking file I/O and user input during that time
• consider reducing the artificial delay we now put onto process spawning