Update StartupAnalyzer to recommend calling UseStatusCodePages after UseRouting

As a follow up to https://github.com/dotnet/aspnetcore/pull/38509, we should add a startup analyzer that recommends ordering `UseStatusCodePages` after `UseRouting` . This is somewhat contingent on https://github.com/dotnet/aspnetcore/issues/38590 being done as we really don't want this analysis to start appearing for apps targeting .net6 or earlier (which is what would happen if we add new rules to the ones shipping via the SDK).