Update .NET SDK Acquisition Support to use the preview APIs for C#

Refer [spec](https://github.com/dotnet/vscode-dotnet-runtime/blob/db9e1c86a0df7690d39c4a60ee34c910ebcea28d/Documentation/global-installs/global-devkit-adoption-plan.md) and [AB](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1816236).