Instead of adding new kind of types, we'll use flag to disambiguate
usual types from unsigned ones, this approach has two advantages:
- less changes in the metadata format
- it allows naturally extend format for unsigned arrays,
which will be supported later
#KT-25310 Fixed
#KT-25273 Fixed
Rework backing field generation logic in PropertyCodegen to switch the
ClassBuilder instance for a multifile part to that of the corresponding facade
class. This became needed because multifile parts, and their metadata, are
generated _before_ the multifile facade class and otherwise we would never
record that there's a synthetic '$annotations' method for a const val and would
not write that to the protobuf message for the property.
See also bad83200
#KT-10892 Fixed
