Consider outer classes when topsorting hierarchy

- when building a topsorted hierarchy, consider not only edges to the class'
  superclasses, but also from inner/nested classes to their container. This
  effectively means that a class cannot inherit from its nested class. Similar
  cases (see the tests) are disallowed in Java.
- filter classes by their presence in TopDownAnalysisContext, not by being a
  MutableClassDescriptor (otherwise analysis for local classes ends up trying
  to do something with outer superclasses)
- delete outdated comment: topsort is needed not only for better diagnostics,
  but also for correct order of fake overrides construction

compiler/testData/diagnostics/tests/cyclicHierarchy/classInheritsNested.kt

@@ -0,0 +1,3 @@
+open class E : <!CYCLIC_INHERITANCE_HIERARCHY!>E.EE<!>() {
+    open class EE
+}