Do not return nested/local classes as a part of package fragment

#KT-13757 Fixed

compiler/testData/compileKotlinAgainstCustomBinaries/prohibitNestedClassesByDollarName/library/test/JavaOuter.java

@@ -0,0 +1,5 @@
+package test;
+
+public class JavaOuter {
+    public static class JavaNested {}
+}

compiler/testData/compileKotlinAgainstCustomBinaries/prohibitNestedClassesByDollarName/library/test/Outer.kt

@@ -0,0 +1,5 @@
+package test
+
+class Outer {
+    class Nested
+}