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

tests/compiler/dart2js/cps_ir/expected/supercall_3.js

+// Expectation for test: 
+// class Base {
+//   var field = 123;
+// }
+// class Sub extends Base {
+//   m(x) => x + super.field;
+// }
+// main() {
+//   print(new Sub().m(10));
+// }
+
+function() {
+  var v0 = "" + (10 + V.Sub$().field);
+  if (typeof dartPrint == "function")
+    dartPrint(v0);
+  else if (typeof console == "object" && typeof console.log != "undefined")
+    console.log(v0);
+  else if (!(typeof window == "object")) {
+    if (!(typeof print == "function"))
+      throw "Unable to print message: " + String(v0);
+    print(v0);
+  }
+}