Add test on rewrite at slice FUNCTOR

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/rewriteAtSliceFunctor.kt

@@ -0,0 +1,10 @@
+// See KT-28847
+
+class Foo(val str: String?) {
+    val first = run {
+        str.isNullOrEmpty()
+        second
+    }
+
+    val second = str.isNullOrEmpty()
+}