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

tests/compiler/dart2js/cps_ir/input/argument_refinement_26.dart

Index: tests/compiler/dart2js/cps_ir/input/argument_refinement_26.dart
diff --git a/tests/compiler/dart2js/cps_ir/input/argument_refinement_26.dart b/tests/compiler/dart2js/cps_ir/input/argument_refinement_26.dart
new file mode 100644
index 0000000000000000000000000000000000000000..dfdd56ba7891af4de6e58bb3bd69183c8c0bb906
--- /dev/null
+++ b/tests/compiler/dart2js/cps_ir/input/argument_refinement_26.dart
@@ -0,0 +1,12 @@
+main() {
+  var x = int.parse('1233');
+  var y = int.parse('1234');
+  var z = int.parse('1235');
+  print(x is int);
+  print(y is int);
+  print(z is int);
+  print(x.modPow(y, z));
+  print(x is int);
+  print(y is int);
+  print(z is int);
+}