[JS IR] add a flag which enable safe property access

If an accessor is not available at runtime we fall back
to the property access.

This is useful in cases when JS objects are casted to Kotlin
classes implicitly. This pattern did work in the old BE, which
lead to a significant amount of code which doesn't work anymore.

libraries/stdlib/js-ir/runtime/kotlinJsHacks.kt

@@ -13,6 +13,17 @@ internal fun <T : Enum<T>> enumValuesIntrinsic(): Array<T> =
 internal fun <T : Enum<T>> enumValueOfIntrinsic(@Suppress("UNUSED_PARAMETER") name: String): T =
     throw IllegalStateException("Should be replaced by compiler")
 
+@PublishedApi
+internal fun safePropertyGet(self: dynamic, getterName: String, propName: String): dynamic {
+    val getter = self[getterName]
+    return if (getter != null) getter.call(self) else self[propName]
+}
+
+@PublishedApi
+internal fun safePropertySet(self: dynamic, setterName: String, propName: String, value: dynamic) {
+    val setter = self[setterName]
+    if (setter != null) setter.call(self, value) else self[propName] = value
+}
 
 /**
  * Implements annotated function in JavaScript.