tests: Copy stdlib tests from Kotlin/JVM

This patch copies Kotlin/JVM stdlib tests (libraries/stdlib/test)
excepting ones with explicit java dependencies. It also transforms
the tests to use them as box-tests.

backend.native/tests/external/stdlib/collections/CollectionTest/reduceIndexed.kt

@@ -0,0 +1,22 @@
+import kotlin.test.*
+import kotlin.comparisons.*
+
+fun box() {
+    expect("123") {
+        val list = listOf("1", "2", "3", "4")
+        list.reduceIndexed { index, a, b -> if (index == 3) a else a + b }
+    }
+
+    expect(5) {
+        listOf(2, 3).reduceIndexed { index, acc: Number, e ->
+            assertEquals(1, index)
+            assertEquals(2, acc)
+            assertEquals(3, e)
+            acc.toInt() + e
+        }
+    }
+
+    assertFailsWith<UnsupportedOperationException> {
+        arrayListOf<Int>().reduceIndexed { index, a, b -> a + b }
+    }
+}