The main problem of the previous approach was that we were only generating
erased method signatures, which was incorrect in case a class also had a member
from another supertype with the same signature as the substituted one from the
collection. Javac issues compilation errors when compiling Java code against
such classes.
Also all the needed method stub signatures were hardcoded in
generateBuiltInMethodStubs() and the case of MutableListIterator was missing
Don't use CodegenUtil#getDeclaredFunctionByRawSignature because it's incorrect
in case of platform types. Instead use JetTypeMapper to find JVM signatures of
methods which are callable on the current class
#KT-6042 Fixed
