backend/tests: Add blackbox tests from Kotlin JVM

Added tests from testData/codegen/box directory. There are blackbox tests
in other directories and they are to be added.

backend.native/tests/external/codegen/blackbox/classes/classObjectAsStaticInitializer.kt

@@ -0,0 +1,19 @@
+var global = 0;
+
+class C {
+  companion object {
+      init {
+        global = 1;
+      }
+  }
+}
+
+fun box(): String {
+  if (global != 0) {
+    return "fail1: global = $global"
+  }
+
+  val c = C()
+  if (global == 1) return "OK" else return "fail2: global = $global"
+}
+