Allow to fork utility process from a worker thread

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](https://github.com/microsoft/vscode/blob/b0b73ee333534add58d2fe48dc48b46b3533a221/src/vs/workbench/services/sharedProcess/electron-sandbox/sharedProcessService.ts#L35-L42) we now put onto process spawning