Reorganize stdlib-js sources specific to the current JS backend

Move kotlin-stdlib-js project and the sources specific to the current backend to 'stdlib/js-v1' directory,
but leave sources that can be shared with the new IR backend in the common 'stdlib/js' location
with exception for 'stdlib/js/src/generated', which is used exclusively for current backend.
This simplifies sourceset configuration when building stdlib with the new backend.

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

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.js
+
+@PublishedApi
+internal fun <T : Enum<T>> enumValuesIntrinsic(): Array<T> =
+    throw IllegalStateException("Should be replaced by compiler")
+
+@PublishedApi
+internal fun <T : Enum<T>> enumValueOfIntrinsic(name: String): T =
+    throw IllegalStateException("Should be replaced by compiler")