[Invariant Fix] Adjust DataFlowValue::Identifier for refinement

After refinement is introduced it becomes possible to have a different
descriptors instances for effectively the same descriptors

Also, it accidentally fixes KT-25432 because is caused by a different
version of descriptors created for NewCapturedType

^KT-25432 Fixed

compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/40.kt

@@ -18,7 +18,7 @@
 fun case_1(x: Pair<*, *>) {
     if (x.first !is String) return
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>
-    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>.<!UNRESOLVED_REFERENCE!>length<!>
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?"), SMARTCAST_IMPOSSIBLE!>x.first<!>.length
 }
 
 /*
@@ -28,5 +28,5 @@ fun case_1(x: Pair<*, *>) {
 fun case_2(x: Pair<*, *>) {
     if (x.first !is String?) throw Exception()
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>
-    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>?.<!UNRESOLVED_REFERENCE!>length<!>
-}
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?"), SMARTCAST_IMPOSSIBLE!>x.first<!>?.length
+}