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/TuplesTest/pairHashSet.kt

@@ -0,0 +1,12 @@
+import kotlin.test.*
+import kotlin.test.assertTrue
+import kotlin.test.assertEquals
+import kotlin.test.assertNotEquals
+
+val p = Pair(1, "a")
+val t = Triple(1, "a", 0.07)
+fun box() {
+    val s = hashSetOf(Pair(1, "a"), Pair(1, "b"), Pair(1, "a"))
+    assertEquals(2, s.size)
+    assertTrue(s.contains(p))
+}