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

tests/compiler/dart2js/cps_ir/expected/argument_refinement_21.js

+// Expectation for test: 
+// main() {
+//   var x = int.parse('1233');
+//   var y = int.parse('1234');
+//   print(x / 2);
+//   print(x is num);
+//   print(y is num);
+//   print(x.compareTo(y));
+//   print(y is num);
+// }
+
+function() {
+  var x = P.int_parse("1233", null, null), y = P.int_parse("1234", null, null), v0 = typeof y === "number";
+  P.print(J.$div$n(x, 2));
+  P.print(true);
+  P.print(v0);
+  if (!v0)
+    throw H.wrapException(H.argumentErrorValue(y));
+  if (x < y)
+    v0 = -1;
+  else if (x > y)
+    v0 = 1;
+  else if (x === y) {
+    v0 = x === 0;
+    v0 = v0 ? (y === 0 ? 1 / y < 0 : y < 0) === (v0 ? 1 / x < 0 : x < 0) ? 0 : (v0 ? 1 / x < 0 : x < 0) ? -1 : 1 : 0;
+  } else
+    v0 = isNaN(x) ? isNaN(y) ? 0 : 1 : -1;
+  P.print(v0);
+  P.print(true);
+}