Variance checker: add check for nested local / anonymous classes

So #KT-16136 Fixed

idea/testData/inspections/addVarianceModifier/nestedAnonymous.kt

@@ -0,0 +1,26 @@
+class C<T> {
+    private val blah = object {
+        fun foo(): T = TODO()
+    }
+
+    fun bar(x: T) {}
+}
+
+class CC<T> {
+    fun some(a: Any = object {
+        fun bar(): T = TODO()
+    }) {}
+
+    fun baz(arg: T) {}
+}
+
+interface G
+
+class CCC<T> : G by object : G {
+    fun some(a: Any = object {
+        fun bar(): T = null!!
+    }) {}
+} {
+    fun baz(arg: T) {}
+}
+