Native: make forward declarations expect in metadata compilations

If we are compiling metadata, make synthetic forward declarations
`expect`, because otherwise `getFirstClassifierDiscriminateHeaders`
would prefer it over a "real" `expect` declaration from a commonized
interop library, which would ruin the whole idea of using synthetic
forward declarations only when no proper definitions are found.

^KT-51377 Fixed

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/TopDownAnalyzerFacadeForKonan.kt

@@ -41,7 +41,8 @@ internal object TopDownAnalyzerFacadeForKonan {
 
         val resolvedModuleDescriptors = nativeFactories.DefaultResolvedDescriptorsFactory.createResolved(
                 config.resolvedLibraries, projectContext.storageManager, module.builtIns, config.languageVersionSettings,
-                config.friendModuleFiles, config.resolve.includedLibraries.map { it.libraryFile }.toSet(), listOf(module))
+                config.friendModuleFiles, config.resolve.includedLibraries.map { it.libraryFile }.toSet(), listOf(module),
+                isForMetadataCompilation = config.metadataKlib)
 
         val additionalPackages = mutableListOf<PackageFragmentProvider>()
         if (!module.isNativeStdlib()) {