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

tests/compiler/dart2js/cps_ir/input/constructor_5.dart

+foo(x) {
+  print(x);
+}
+class Base {
+  var x1 = foo('x1');
+  var x2;
+  var x3 = foo('x3');
+  Base() : x2 = foo('x2');
+}
+class Sub extends Base {
+  var y1 = foo('y1');
+  var y2;
+  var y3;
+  Sub() : y2 = foo('y2'), super(), y3 = foo('y3');
+}
+main() {
+  new Sub();
+}
+