[electron-updater] `spawnSyncLog` blocks the main thread resulting in frozen apps during auto update

[aortbals]

Running quitAndInstall will trigger the auto update process while an app is open. When triggering this from Ubuntu (this happens on other distros too, just not as glaring), it typically runs a dpkg command to install the package while the app is open. Because this blocks the main thread, it causes the entire app to hang, and a "Force quit" dialog will appear in Ubuntu. In the case of the user, it feels as if the update is failed. It will complete eventually, but if they force quit it kills the dpkg process, failing the update and also screwing up the underlying dpkg requiring sudo dpkg --configure -a to restore it.

Can we consider making the update process async?

Here is an example of the issue. It can take a minute or two for an update to complete.

[mmaietta]

Async auto-update installations have been explored before, however, there's no callback IIRC to catch when an installation has actually finished. I don't think this is possible to achieve (it might be worth noting that before the synchronous implementations on linux, linux autoupdate for non-AppImage didn't even exist)
Most recent investigation stalled as well: #8405