Most of these tests check the specific structure of lambdas when they
are generated as classes, and they start to fail once invokedynamic
lambdas are enabled by default.
- Uncomment tests
- Add proper visibility to companion field
+ Make exception for interfaces -> they need to respect language versions 1.8
before they can put private members there.
- Adjust synthetic accessor lowering to look for enclosing classes with access
via companion object.