Restart automatically on extension update when nothing open / welcome page

[RinCat]

We already have #214424, and it is understandable that it can cause problems during active use.

But I often face that I opened vscode before I decided which project to open, the extension update already downloaded. And I will click "Restart Extensions" before opening anything. In this case, and I think it will occur very often, restart updated extensions should be very safe compared to restart after open a project.

So, I think automatic restart on empty / welcome page should be a thing before the more complex one is finished.