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

tests/compiler/dart2js/cps_ir/input/constructor_3.dart

+class Base0 {
+  Base0() {
+    print('Base0');
+  }
+}
+class Base extends Base0 {
+  var x;
+  Base(this.x);
+}
+class Sub extends Base {
+  var y;
+  Sub(x, this.y) : super(x) {
+    print(x);
+  }
+}
+main() {
+  print(new Sub(1, 2).x);
+}