Make it so that we can console.log in browser to debug gentest (#1718)

Summary:

Our gentest works by console.logging the contents of the test it is generating to the browser powered by the driver. The driver then reads the logs and writes it to a file. An unfortunate side effect here is that we cannot console.log to debug how the gentest logic actually works since the driver is expecting formatted code. To get around this I had the driver filter out logs with a certain prefix and add that a helper that logs a message with this prefix to the scripts.

Reviewed By: NickGerleman

Differential Revision: D64011035

gentest/gentest-log.js

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// eslint-disable-next-line no-unused-vars
+function gentestLog(message) {
+  console.log('gentest-log: ', message);
+}