FIR checker: fix position strategy for UNRESOLVED_LABEL

compiler/testData/diagnostics/tests/labels/labeledFunctionLiteral.fir.kt

@@ -1,17 +1,17 @@
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 
 val funLit = lambda@ fun String.() {
-    val d1 = <!UNRESOLVED_LABEL!>this@lambda<!>
+    val d1 = this<!UNRESOLVED_LABEL!>@lambda<!>
 }
 
 fun test() {
     val funLit = lambda@ fun String.(): <!UNRESOLVED_LABEL!>String<!> {
-        return <!UNRESOLVED_LABEL!>this@lambda<!>
+        return this<!UNRESOLVED_LABEL!>@lambda<!>
     }
 }
 
 fun lambda() {
     val funLit = lambda@ fun String.(): <!UNRESOLVED_LABEL!>String<!> {
-        return <!UNRESOLVED_LABEL!>this@lambda<!>
+        return this<!UNRESOLVED_LABEL!>@lambda<!>
     }
-}
+}