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

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt

@@ -119,6 +119,9 @@ class DirectoryBasedClassFinder(
     // TODO
     override fun findMetadata(classId: ClassId): InputStream? = null
 
+    // TODO
+    override fun hasMetadataPackage(fqName: FqName): Boolean = false
+
     // TODO: load built-ins from packageDirectory?
     override fun findBuiltInsData(packageFqName: FqName): InputStream? = null
 }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/vfilefinder/fileFinders.kt

@@ -59,6 +59,9 @@ class JvmIDEVirtualFileFinder(private val scope: GlobalSearchScope) : VirtualFil
     // TODO
     override fun findMetadata(classId: ClassId): InputStream? = null
 
+    // TODO
+    override fun hasMetadataPackage(fqName: FqName): Boolean = false
+
     // TODO: load built-ins metadata from scope
     override fun findBuiltInsData(packageFqName: FqName): InputStream? = null