explore the new Password APIs for storing passwords

[GitMensch]

As the Password APIs are still part of the "Proposed extension APIs" these seem to not be useable in master yet. I guess it still would be reasonable to inspect those in a branch now, allowing to give feedback as long as those are "proposed" and pull the trigger to master once they are moved to stable.

[GitMensch]

OK, so obviously they are no longer "proposed" but final now with microsoft/vscode@67ded11 (Feb 2021). Therefore I suggest inspecting it and use if possible.