Expose DriverTracer factory methods

[andresmgot]

Hi 👋

I am using this driver but since we have our own implementation to handle AWS connections, I'm just using the Rows struct to parse responses from Athena. In particular, I am using the NewRows function. The problem is that the function requires a *DriverTracer instance but there is no way to create that outside this package.

The methods to create a *DriverTracer are there but they are unexported. Can I send a PR to expose them so I can use NewRows directly?

Thanks!