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/contains.kt

@@ -0,0 +1,11 @@
+import kotlin.test.*
+import kotlin.comparisons.*
+
+fun <T> Iterable<T>.toIterable(): Iterable<T> = Iterable { this.iterator() }
+
+fun box() {
+    assertFalse(hashSetOf<Int>().contains(12))
+    assertTrue(listOf(15, 19, 20).contains(15))
+
+    assertTrue(hashSetOf(45, 14, 13).toIterable().contains(14))
+}