vsls:/ URIs are converted to file:/ URIs on the way to analysis server, causes issues with Live Share

If you open a project in Live Share, we get a root folder of `vsls:/`, but this code here converts it to `file:///`:

https://github.com/Dart-Code/Dart-Code/blob/a895d3ca437bca7520e2abb9c2ce87f4220a9eb9/src/extension/analysis/analyzer_lsp.ts#L421

This results in the server analyzing the entire disk.