Way to discover remote authority in empty window

E.g.: As a UI extension, Remote-Containers has no way of discovering with which WSL distro an empty window is connected with. When there is a folder open, that folder's URI can be used, but in an empty window there is only vscode.env.remoteName and that is only 'wsl'. (Remote-Containers would use this to use WSL's Docker CLI when connected with Remote-WSL. microsoft/vscode-remote-release#3534) /cc @aeschli