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/maxBy.kt

@@ -0,0 +1,12 @@
+import kotlin.test.*
+import kotlin.comparisons.*
+
+fun box() {
+    expect(null, { listOf<Int>().maxBy { it } })
+    expect(1, { listOf(1).maxBy { it } })
+    expect(2, { listOf(2, 3).maxBy { -it } })
+    expect('b', { listOf('a', 'b').maxBy { "x$it" } })
+    expect("abc", { listOf("b", "abc").maxBy { it.length } })
+    expect(null, { listOf<Int>().asSequence().maxBy { it } })
+    expect(2, { listOf(2, 3).asSequence().maxBy { -it } })
+}