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

tests/compiler/dart2js/cps_ir/input/argument_refinement_num_16.dart

Index: tests/compiler/dart2js/cps_ir/input/argument_refinement_num_16.dart
diff --git a/tests/compiler/dart2js/cps_ir/input/argument_refinement_num_16.dart b/tests/compiler/dart2js/cps_ir/input/argument_refinement_num_16.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c757d081848091753f5bb67dae593b474c3e8e5d
--- /dev/null
+++ b/tests/compiler/dart2js/cps_ir/input/argument_refinement_num_16.dart
@@ -0,0 +1,9 @@
+main() {
+  var x = int.parse('1233');
+  var y = int.parse('1234');
+  print(x is num);
+  print(y is num);
+  print(x + y);
+  print(x is num);
+  print(y is num); // will stay as is-num because String could be a target of +
+}