Make erasure insert `.package` in referneces
Treat  i0239 specially. It shows some problems that could be of interest.
Refactored common behavior from TypeAssigner and TypeErasure
Simplified and commented makePackageObjPrefixExplicit
Merge pull request #303 from dotty-staging/fix-packageObjects-members-erasure

Make erasure insert `.package` in TermRefs to members of package object.