Do not drop analysis results for the code fragment context, allow to re-use it

Otherwise labels declared in the expression context become unresolved.
This is needed for the `this@label` expression evaluation support (KT-28134).

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/LabelResolver.kt

@@ -41,7 +41,7 @@ object LabelResolver {
             if (name != null && name == labelName) {
                 elements.add(getExpressionUnderLabel(parent as KtExpression))
             }
-            parent = parent.parent
+            parent = if (parent is KtCodeFragment) parent.context else parent.parent
         }
         return elements
     }