cpsir unittests: move all unittests into individual files and test runners.

tests/compiler/dart2js/cps_ir/expected/control_flow_8.js

+// Expectation for test: 
+// main() {
+//   var list = [1,2,3,4,5,6];
+//   for (var x in list) {
+//     print(x);
+//   }
+// }
+
+function() {
+  var list = [1, 2, 3, 4, 5, 6], i = 0, line;
+  for (; i < 6; ++i) {
+    line = H.S(list[i]);
+    if (typeof dartPrint == "function")
+      dartPrint(line);
+    else if (typeof console == "object" && typeof console.log != "undefined")
+      console.log(line);
+    else if (!(typeof window == "object")) {
+      if (!(typeof print == "function"))
+        throw "Unable to print message: " + String(line);
+      print(line);
+    }
+  }
+}