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

tests/compiler/dart2js/cps_ir/expected/closures_5.js

+// Expectation for test: 
+// main() {
+//   var x = 122;
+//   var a = () => x;
+//   x = x + 1;
+//   print(a());
+// }
+
+function() {
+  var _captured_x_0 = 122 + 1, line = _captured_x_0 === 0 ? 1 / _captured_x_0 < 0 ? "-0.0" : "" + _captured_x_0 : "" + _captured_x_0;
+  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);
+  }
+}