Preserve view state for untitled files between restarts

[jrieken]

re #16544

• have an untitled file, select a word on line 13
• exit, restart
• 🐛 the cursor isn't preserved and not at 1,1

[bpasero]

There is actually no view-state preserved for untitled files because we never had untitled files surviving a restart.

[bpasero]

I wanna check if this is low hanging for November, otherwise I will push it out.

[bpasero]

Will do in January, it is just a matter of persisting our untitled view state that we already track in https://github.com/Microsoft/vscode/blob/master/src/vs/workbench/browser/parts/editor/stringEditor.ts#L36