Fix reflection on top level declarations from other modules

The main problem here is that moduleName that is being passed to KPackageImpl
is useless: as can be seen in
ClosureCodegen.generateCallableReferenceDeclarationContainer, the name of the
current module is always written to the class file for a callable reference,
not the name of the module of the referenced declaration. This resulted in
reflection not loading the correct .kotlin_module file and subsequently not
finding the required file facade for a top-level function.

The commit does not fix the issue with the incorrect module name written in the
back-end, but workarounds it. It turns out, reflection can figure out the name
of the module of the referenced declaration itself by parsing the header from
the given java.lang.Class object for a single-file/multi-file package facade
and extract the package_module_name protobuf extension. Similar code was
already there in Member.getKPackage() in ReflectJvmMapping.kt but it did not
support multi-file classes, of which there are a lot in the standard library;
this is now supported

 #KT-12630 Fixed
 #KT-14731 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/ClosureCodegen.java

@@ -396,6 +396,9 @@ public class ClosureCodegen extends MemberCodegen<KtElement> {
         }
         else if (container instanceof PackageFragmentDescriptor) {
             iv.aconst(state.getTypeMapper().mapOwner(descriptor));
+            // Note that this name is not used in reflection. There should be the name of the referenced declaration's module instead,
+            // but there's no nice API to obtain that name here yet
+            // TODO: write the referenced declaration's module name and use it in reflection
             iv.aconst(state.getModuleName());
             iv.invokestatic(REFLECTION, "getOrCreateKotlinPackage",
                             Type.getMethodDescriptor(K_DECLARATION_CONTAINER_TYPE, getType(Class.class), getType(String.class)), false);