Introduce KotlinMetadataFinder#hasMetadataPackage

Before creating a MetadataPackageFragment, check that the corresponding
directory (across the classpath) contains at least one .kotlin_metadata file.
Otherwise we're creating packages for every simple name queried during the
resolution and sometimes prefer a (empty) package to the existing class, for
example when the latter class is star-imported

core/descriptors.runtime/src/org/jetbrains/kotlin/load/kotlin/reflect/ReflectKotlinClassFinder.kt

@@ -39,6 +39,9 @@ class ReflectKotlinClassFinder(private val classLoader: ClassLoader) : KotlinCla
     // TODO
     override fun findMetadata(classId: ClassId): InputStream? = null
 
+    // TODO
+    override fun hasMetadataPackage(fqName: FqName): Boolean = false
+
     // TODO: load built-ins from classLoader
     override fun findBuiltInsData(packageFqName: FqName): InputStream? = null
 }