The idea here is... if a token is currently being refreshed, well then getting a token of those scopes should wait for that to finish.
Core has a really nice `SequencerByKey` for exactly this kind of thing, and so I've stolen that and started to organize the code with a `common` folder.
Oh, I also noticed we were sorting twice and fixed that to only sort once.
ref https://github.com/microsoft/vscode/issues/186693
41e940f76f