Generated public auto interfaces are inherited from IAutoInterface and IAutoInterface<T> to allow constraint type restrictions.
Attributes moved from generated code to separate project (and nuget package), to allow inherited from GenerateAutoInterfaceAttribute classes to be used in linked projects. That package must be installed independently.
Generated files are marked with // <auto-generated/> to turn off warnings.
Enabled #nullable for generated files.
Added support for nested types, example:
  class A { public int A { get; } }
  [GeneratedAutoInterface] class B : A { }
will generate:
  interface IB { int A { get; } }