Logging from inside goja or otto transform functions

[pranaygp]

There doesn't seem to be a way to log anything from inside a javascript transform function. This would be tremendously useful for debugging the transform code.

We're also trying to use this as a way to have performance benchmarks across our entire data pipeline on Windsor, a piece of which involves using transporter.

I'd like to log the ID for some of the messages being synced by transporter and figured doing it from inside a transform would be a good place.

cc @atfaust2