LambdaLift lifts methods that access private fields too far

[DarkDimius]

Contexts.Context.printCreationTraces has a lambda inside, that accesses a private accessor creationTrace of Contexts.Context.
LambdaLift lifts it out to a static method in Contexts, without setting a NotJavaPrivate on the private accessor of the creationTrace.

Manifests itself with such error:

Exception in thread "main" java.lang.VerifyError: Bad invokespecial instruction: current class isn't assignable to reference class.
Exception Details:
  Location:
    dotty/tools/dotc/core/Contexts$.$anonfun$printCreationTraces$2(Ldotty/tools/dotc/core/Contexts$$Context;)V @50: invokespecial
  Reason:
    Error exists in the bytecode

[DarkDimius]

@odersky If you decide that you can lift method to be static, why make it static on top-level class, instead of making it static on the class that was the original owner?

[odersky]

Addressed by #517