Add test for for kt42457 wrong behaviour. Align runtime concatenation with it

#KT-42457

compiler/testData/codegen/box/strings/kt42457_old.kt

@@ -0,0 +1,17 @@
+// TARGET_BACKEND: JVM
+// FILE: JavaClass.java
+
+public class JavaClass {
+    public String toString() {
+        return null;
+    }
+}
+
+// FILE: Kotlin.kt
+fun box(): String {
+    val toString: String? = JavaClass().toString()
+    if (toString != null) return "fail 1: $toString"
+    val template: String? = "${JavaClass()}"
+    if (template != null) return "fail 2: $template"
+    return "OK"
+}