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/SetOperationsTest/distinct.kt

@@ -0,0 +1,7 @@
+import kotlin.test.*
+
+
+fun box() {
+    assertEquals(listOf(1, 3, 5), listOf(1, 3, 3, 1, 5, 1, 3).distinct())
+    assertTrue(listOf<Int>().distinct().isEmpty())
+}