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

tests/compiler/dart2js/cps_ir/expected/basic_2.js

+// Expectation for test: 
+// foo(a, [b = "b"]) { print(b); return b; }
+// bar(a, {b: "b", c: "c"}) { print(c); return c; }
+// main() {
+//   foo(0);
+//   foo(1, 2);
+//   bar(3);
+//   bar(4, b: 5);
+//   bar(6, c: 7);
+//   bar(8, b: 9, c: 10);
+// }
+
+function() {
+  P.print("b");
+  P.print(2);
+  P.print("c");
+  P.print("c");
+  P.print(7);
+  P.print(10);
+}