3.4.0

• Upgrade from Roslyn 3.11.0 to 5.3.0
• MEN020 improvements:
  • Improve nullability analysis using latest Roslyn API
  • Treat out var as evident in "static bool T.Method(…, out T)"
  • Infer evident types through awaitables
• Use semantic model to simplify MEN013
• A few more code modernization tweaks