Without this commit, JVM name mapping logic in BE does not work for FIR,
because FIR cannot use old BuiltInsPackageFragmentImpl descriptor.
In this commit we add our own implementation thus fixing
a pack of FIR black box tests.
There are cases when members deserialized from JVM classes have no JVM
signature in the proto. For example, if a member is inherited from a
built-in class (such as Map.getOrDefault in some Map implementations),
or if a member is synthesized in the compiler front-end and back-end
separately (such as enum values/valueOf). In these cases, we'll use the
naive type mapping to try to recover the signature.
#KT-16616 Fixed
#KT-17542 Fixed
Vitaly