KT-6628 Allow imports of classes from root package

#KT-6628 Fixed

compiler/testData/diagnostics/tests/imports/ImportFromRootPackage.kt

@@ -0,0 +1,25 @@
+// FILE: rootPackage.kt
+class Klass {
+}
+
+fun function() = ""
+
+val property = ""
+
+// FILE: anotherFromRootPackage.kt
+fun foo(): Klass {
+    function() + property
+    return Klass()
+}
+
+// FILE: anotherFromRootPackage.kt
+package pkg
+
+import Klass
+import function
+import property
+
+fun foo(): Klass {
+    function() + property
+    return Klass()
+}