Fix isInitialized for companion lateinit properties

Instead of trying to access a missing field `Foo.foo`, call the
synthetic accessor `Foo.access$getFoo$cp` which, as per previous commit,
no longer contains the lateinit assertion

 #KT-21862 Fixed

compiler/testData/codegen/box/properties/lateinit/isInitializedAndDeinitialize/companionObjectField.kt

@@ -0,0 +1,41 @@
+// WITH_RUNTIME
+
+class Class {
+    companion object {
+        lateinit var public: String
+        private lateinit var private: String
+
+        fun test() {
+            if (::public.isInitialized) throw AssertionError("Fail 1")
+            public = "OK"
+            if (public != "OK") throw AssertionError("Fail 2")
+
+            if (::private.isInitialized) throw AssertionError("Fail 3")
+            private = "OK"
+            if (private != "OK") throw AssertionError("Fail 4")
+        }
+    }
+}
+
+class Interface {
+    companion object {
+        lateinit var public: String
+        private lateinit var private: String
+
+        fun test() {
+            if (::public.isInitialized) throw AssertionError("Fail 5")
+            public = "OK"
+            if (public != "OK") throw AssertionError("Fail 6")
+
+            if (::private.isInitialized) throw AssertionError("Fail 7")
+            private = "OK"
+            if (private != "OK") throw AssertionError("Fail 8")
+        }
+    }
+}
+
+fun box(): String {
+    Class.test()
+    Interface.test()
+    return "OK"
+}