[SLC] Add SLC structure tests for nested classes

^KT-62038

analysis/symbol-light-classes/testData/structure/NestedClasses.kt

@@ -0,0 +1,17 @@
+open class A {
+    class NestedInA {
+        open class NestedInNestedInA
+
+        inner class InnerInNestedInA
+    }
+
+    inner class InnerInA {
+        inner class InnerInInnerInA
+    }
+}
+
+class B : A() {
+    class NestedInB : NestedInA.NestedInNestedInA()
+
+    inner class InnerInB
+}