The initial intention for this change was to disallow users to open a
codespace in VS Code if the codespace has a pending operation. This also
adds a side-benefit of presenting the user an error before waiting for
VS Code to open if they provide an invalid codespace to open.
The `codespace code` command used the `skratchdot/open-golang` library
to open `vscode://` URLs, which uses `xdg-open` for Linux under the
hood, which isn't available under WSL.
This switches over to using the `cli/browser` package which has explicit
support for WSL by invoking `wslview` when found.
