unit-tests: Simple support for test classes

backend.native/tests/testing/smoke.kt

@@ -1,4 +1,5 @@
 import kotlin.test.Test
+import konan.test.*
 
 class A {
     @Test
@@ -7,8 +8,17 @@ class A {
     }
 }
 
-@Test
-fun test() {
-    println("test")
-}
+//abstract class AA<T> {
+//    abstract fun a(): T
+//}
+//
+//
+//class BB: AA<Int>() {
+//    override fun a() = 5
+//}
+
+//@Test
+//fun test() {
+//    println("test")
+//}