Convert Mojo tests to use swarming.

testing/test.gni

Index: testing/test.gni
diff --git a/testing/test.gni b/testing/test.gni
index 0a6b98674a8ae5d3d813ce7f50781de5ace46e03..650940e69744d9121373922ed4241e316b3fc27a 100644
--- a/testing/test.gni
+++ b/testing/test.gni
@@ -338,5 +338,14 @@ template("test") {
         ":${invoker.target_name}",
       ]
     }
+
+    if (defined(invoker.output_name) && target_name != invoker.output_name) {
+      group("${invoker.output_name}_run") {
+        testonly = true
+        deps = [
+          ":${invoker.target_name}",
+        ]
+      }
+    }
   }
 }