Update almost all tests (except co19) to use the new try-catch syntax.

tests/lib/math/math2_test.dart

Index: tests/lib/math/math2_test.dart
diff --git a/tests/lib/math/math2_test.dart b/tests/lib/math/math2_test.dart
index 54687b93466f05ae4e390342065b00e2b83e0049..cf71142d7ca27305129c0e9ecdfe7e96b5c1d470 100644
--- a/tests/lib/math/math2_test.dart
+++ b/tests/lib/math/math2_test.dart
@@ -158,7 +158,7 @@ class MathLibraryTest {
     try {
       math.parseInt(str);
       return false;
-    } catch (FormatException e) {
+    } on FormatException catch (e) {
       return true;
     }
   }