[FIR2IR] Process anonymous object nested classes correctly

#KT-42373 Fixed

compiler/testData/ir/irText/firProblems/InnerClassInAnonymous.kt

@@ -0,0 +1,14 @@
+fun box(): String {
+    val obj = object {
+        val end = "K"
+
+        fun foo() = Some("O").bar()
+
+        inner class Some(s: String) : Base(s) {
+            fun bar() = s + end
+        }
+
+        open inner class Base(val s: String)
+    }
+    return obj.foo()
+}