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/MapTest/getOrElse.kt

@@ -0,0 +1,22 @@
+import kotlin.test.*
+
+
+fun box() {
+    val data = mapOf<String, Int>()
+    val a = data.getOrElse("foo") { 2 }
+    assertEquals(2, a)
+    val a1 = data.getOrElse("foo") { data.get("bar") } ?: 1
+    assertEquals(1, a1)
+
+    val b = data.getOrElse("foo") { 3 }
+    assertEquals(3, b)
+    assertEquals(0, data.size)
+
+    val empty = mapOf<String, Int?>()
+    val c = empty.getOrElse("") { null }
+    assertEquals(null, c)
+
+    val nullable = mapOf(1 to null)
+    val d = nullable.getOrElse(1) { "x" }
+    assertEquals("x", d)
+}