Fix nullness flow for type aliases after null pattern#18852

T-Gro merged 14 commits intomaindotnet/fsharp:mainfrom

copilot/fix-af0393e2-3297-4af1-9895-193ff65f32aedotnet/fsharp:copilot/fix-af0393e2-3297-4af1-9895-193ff65f32aeCopy head branch name to clipboard